High ionic conductivity high temperature resistant lithium ion battery separator and preparation method thereof

Abstract

The application discloses a high-ionic-conductivity high-temperature-resistant lithium ion battery diaphragm and a preparation method thereof, and belongs to the technical field of battery diaphragms, and is used for solving the technical problem that the high-temperature resistance and ionic conductivity of the lithium ion battery diaphragm in the prior art need to be further improved. The preparation method of the high-ionic-conductivity high-temperature-resistant lithium ion battery diaphragm comprises the following steps: dissolving polyphthalic amide and modified cellulose into an N,N-dimethylacetamide solution to form a spinning solution, and then adopting electrostatic spinning to prepare a spinning base film with a thickness of 29-31 mu m. After the electrostatic spinning of the polyphthalic amide and the modified cellulose as raw materials, the triazine modification is performed on the spinning base film, and then the inorganic coating liquid is used for coating, so that the mechanical strength and the heat-resistant stability of the battery diaphragm are effectively improved, the ionic conductivity is also improved, and the charging and discharging efficiency of the lithium battery is improved.

Description

TECHNICAL FIELD

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

[0002] As an efficient and environmentally friendly energy storage device, in recent years, with the increasing demand for energy density, safety and cycle life of lithium ion batteries in the fields of new energy vehicles, energy storage systems and consumer electronics, the separator, as one of the key components of the battery, its main function is to separate the positive and negative electrodes to prevent internal short circuit, while allowing lithium ions to pass freely during charging and discharging, and its performance directly affects the key indicators such as capacity, cycle life and safety performance of the battery.

[0003] The lithium ion battery in the prior art will generate a certain amount of heat during charging and discharging, especially when used in high-temperature environments, the temperature inside the battery will rise sharply, and the traditional polyolefin separator has poor thermal stability and is prone to thermal shrinkage or even melting at high temperatures, resulting in direct contact between the positive and negative electrodes, causing internal short circuit of the battery, and further causing thermal runaway, fire or explosion of the battery, and the traditional polyolefin separator, although it has good mechanical properties and chemical stability, due to the characteristics of the material itself, it has poor affinity for electrolyte and low porosity, resulting in large migration resistance of lithium ions in the separator and low ionic conductivity, which makes the battery prone to polarization during high-rate charging and discharging, reducing the performance and life of the battery.

[0004] In view of the technical defects in this regard, a solution is now proposed. SUMMARY

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

[0006] The purpose of the present application can be achieved by the following technical solutions:

[0007] A preparation method of a high-ionic-conductivity high-temperature-resistant lithium ion battery separator, comprising the following steps:

[0008] S1, dissolving polyphthalamide and modified cellulose into N,N-dimethylacetamide solution to form a spinning solution, and then using electrospinning to prepare a spinning base film with a thickness of 29-31 μm;

[0009] S2, immersing the spinning base film into a modification liquid to perform immersion modification on the spinning base film, forming a triazine-modified intermediate layer on the spinning base film, and preparing a modified spinning base film;

[0010] S3, coating the modified spinning base film on both sides with a coating liquid composed of inorganic materials, and after curing, rolling and compacting to prepare a battery separator.

[0011] Further, step S1 is that the spinning base film is processed by the following steps:

[0012] A1, mixing a polyphthalamide, modified cellulose and N,N-dimethylacetamide solution, increasing the temperature of the reaction system to 75-85 DEG C, stirring until the system is dissolved, standing to remove bubbles, to obtain a spinning solution;

[0013] A2, electrospinning the spinning solution by electrospinning to prepare a spinning base film with a thickness of 29-31 mu m.

[0014] Further, 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 DEG C, the spinning solution propelling speed is 1mL / h, the receiving distance is 26-28cm, the spinning voltage is 15kV, after spinning, the spinning base film is transferred to purified water with a temperature of 60-70 DEG C, soaked for 30-50min, washed with purified water for 3 times, then drained, and then transferred to a drying box with a temperature of 60-70 DEG C, dried to constant weight to obtain the spinning base film.

[0015] Further, the preparation method of the modified cellulose is: cellulose and lye are added to the reaction system and stirred and mixed, the temperature of the reaction system is increased to 50-60 DEG C, stirring until the system is dissolved, and then a dodecyl glycidyl ether solution is added to the reaction system, and the reaction is kept for 60-80min, and then treated to obtain the modified cellulose.

[0016] Further, the amount ratio of the cellulose, lye and dodecyl glycidyl ether solution is 5-6g:20-30mL:10-13g, the lye is a 2-3mol / L sodium hydroxide solution, the dodecyl glycidyl ether solution is composed of dodecyl glycidyl ether and N,N-dimethylformamide at 1g:10mL, and the post-treatment includes: after the reaction is completed, the temperature of the reaction system is reduced to room temperature, anhydrous ethanol is added to the reaction system, and then filtered, the filter cake is washed with anhydrous ethanol for 3 times and then drained, the filter cake is transferred to a drying box with a temperature of 60-70 DEG C, and dried to constant weight to obtain the modified cellulose.

[0017] The synthesis reaction mechanism of the modified cellulose is:

[0018]

[0019] wherein, is a simple formula of cellulose;

[0020] During the reaction, in the alkaline environment, the hydroxyl group on the cellulose and the epoxy group on the molecule of dodecyl glycidyl ether open ring condensation to form chemical modification, form dodecyl glycidyl ether modification on the cellulose, and obtain the modified cellulose.

[0021] Further, in step S2, the preparation method of the modified spinning base film is as follows: mixing melamine and N,N-dimethylformamide, increasing the temperature of the reaction system to 55-65℃, stirring until the system is dissolved, adding 3-isocyanate propyl trimethoxysilane to the reaction system, and keeping the reaction for 50-60 min; adding dilute acid to the reaction system, and stirring for 10-15 min to obtain a modified liquid; immersing the spinning base film in the modified liquid, keeping it fully immersed for 40-60 min, and post-treating to obtain the modified spinning base film.

[0022] The synthesis reaction mechanism of the modified spinning base film is as follows:

[0023]

[0024] During the reaction, the isocyanate group on the molecule of 3-isocyanate propyl trimethoxysilane and the amino group on the molecule of melamine condense to form trimethoxysilane modification on the triazine molecular ring, and then under the catalysis of dilute acid, the trimethoxysilane molecule is hydrolyzed to form silanol, thereby obtaining the modified liquid; after the spinning base film is immersed in the modified liquid, the silanol on the molecule of the modified liquid and the active functional groups on the surface of the spinning base film are chemically bonded to form triazine modification on the spinning base film, thereby obtaining the modified spinning base film.

[0025] Further, the amount ratio of the melamine, N,N-dimethylformamide, 3-isocyanate propyl trimethoxysilane and dilute acid is 1 g:30 mL:4.6 g:10 mL, the dilute acid is 0.3-0.6 mol / L hydrochloric acid; the solid-liquid ratio of the spinning base film and the modified liquid is 1:7-8, and the post-treatment includes: after the reaction is completed, the spinning base film is taken out of the modified liquid, washed with purified water until it is neutral, and then drained; the spinning base film is transferred to a drying box with a temperature of 70-80℃, and dried to constant weight to obtain the modified spinning base film.

[0026] Further, the preparation method of the coating liquid is as follows: mixing boehmite, mica powder and purified water, stirring at room temperature for 4-6 h to obtain a mixed liquid, adding KH-560 to the mixed liquid, stirring for 10-20 min, adding the mixed liquid to a high-pressure homogenizer, homogenizing and mixing, adding a binder to the solution, and stirring and mixing for 30-50 min to obtain the coating liquid.

[0027] The synthesis reaction mechanism of the coating liquid is as follows:

[0028] During the reaction, the boehmite and mica powder are mixed, the inorganic particles are surface modified by silane coupling agent KH-560 to form an epoxy group polysiloxane coating on the particles, and then the particles are homogenously mixed by a homogenizer, mixed with the binder to obtain the coating liquid.

[0029] Further, the amount 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 lithiumated polyacrylic acid, the homogenization pressure of the high-pressure homogenizer is 130-150MPa, and the homogenization frequency is 10 times.

[0030] Further, the forming method of the battery separator is as follows: the coating liquid is uniformly coated on both sides of the modified spinning base film at a single-side coating amount of 20-30mL / m 2 After drying, a battery separator crude product is obtained; the battery separator crude product is added to a roller press, the roller pressing temperature is set to 65-75℃, and the battery separator with a thickness of 26-28μm is obtained.

[0031] A high-ionic-conductivity high-temperature-resistant lithium ion battery separator is prepared by a high-ionic-conductivity high-temperature-resistant lithium ion battery separator preparation method.

[0032] The present application has the following advantages:

[0033] 1. The high-ionic-conductivity high-temperature-resistant lithium ion battery separator of the present application uses polyphthalamide and modified cellulose as raw materials, dissolves them in N,N-dimethylacetamide solution to form a spinning solution, and then electrospins the spinning base film, modifies a triazine modification layer on the spinning base film, and then performs surface coating modification by using a coating liquid composed of boehmite and mica powder to form a reinforced coating layer on the surface of the spinning base film, thereby preparing the battery separator.

[0034] 2. The high-ionic-conductivity high-temperature-resistant lithium-ion battery separator of the present application, polyphthalamide as the main film-forming matrix 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, reduces the hydrophilicity of cellulose, changes the surface energy from polarity to non-polarity, better matches the hydrophobic property of polyphthalamide, the residual hydroxyl group forms hydrogen bonds with the amide bond of polyphthalamide to enhance the interfacial adhesion and improve the compatibility of modified cellulose and polyphthalamide, N,N-dimethylacetamide is a good solvent for polyphthalamide, the addition of LiCl helps to destroy the hydrogen bonds between modified cellulose molecules and promote the uniform dispersion of modified cellulose in the polyphthalamide solution, thereby constructing a three-dimensional network cross-linking between molecules, and the long-chain hydrophobic group introduced by dodecyl glycidyl ether reduces the number of cellulose hydroxyl groups and the hydrophilicity of the separator, avoiding excessive swelling of the electrolyte, optimizing the hydrophobic-hydrophilic balance, and facilitating the formation of lithium ion transmission channels.

[0035] 3. The high-ionic-conductivity high-temperature-resistant lithium-ion battery separator of the present application, the spinning base film is modified by immersion in a modification liquid, which allows the modifier to fully penetrate into the pores of the fiber network, and the silanol on the triazine molecule of the modifier can chemically bond with the active reaction sites on the surface of the spinning base film, enhancing the bonding force between fibers, thereby greatly improving the ability of the base film to resist tensile deformation, and the cross-linking makes the entire fiber network more rigid and less prone to plastic deformation, which is beneficial to resist puncture, and the decomposition temperature of melamine as the body of triazine is high, thereby improving the overall heat stability of the base film; after the boehmite and mica powder are surface modified by KH-560, the coating slurry is highly uniformly dispersed through homogeneous dispersion, the modified spinning base film is coated and modified in a coating manner, the epoxy group on the surface of the inorganic particles in the coating liquid can undergo ring-opening condensation with the imino group on the modified triazine modifier molecule of the modified spinning base film, thereby forming a stable modified layer on the modified spinning base film, boehmite and mica powder are both high-temperature-resistant materials, and the cross-linked structure further enhances the thermal stability of the coating layer, reducing high-temperature deformation, and the coating layer is combined more closely with the base film through rolling, improving the overall density, thereby enhancing the mechanical strength, and boehmite and mica powder are inorganic particles, and the porous structure formed after coating and solidification helps to improve the porosity of the separator, thereby increasing the ion transmission channels, and the lithiumated polyacrylic acid as the binder not only has the effect of bonding boehmite and mica powder and other fillers together, but also has ionic conductivity due to the presence of lithium ions, which can further improve the ionic conductivity of the coating layer. DETAILED DESCRIPTION

[0036] The technical solutions of the present application will be clearly and completely described below in conjunction with the embodiments, and obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative efforts belong to the scope of protection of the present application.

[0037] In the present application, the polyphthalamide is selected from Shanghai Chongshi Plastic Co., Ltd., the model is GV-2H, the tensile modulus is 8200 MPa, the transverse shrinkage is 0.8%, the water absorption saturation at 23 DEG C is 5%, the volume resistivity is 1*10 14 Ω*cm, the ball pressure hardness is 225 MPa, and the brand is EMS of Switzerland;

[0038] In the present application, the cellulose is hydroxymethyl cellulose;

[0039] In the present application, the KH-560 is gamma-glycidyl ether propyl trimethoxysilane, and the CAS number is 2530-83-8;

[0040] In the present application, the lithiumated polyacrylic acid is selected from Shenzhen Liyou New Energy Technology Co., Ltd., the model is TOB-PAALi, and the brand is TOB-Liyou.

[0041] Example 1

[0042] The present embodiment provides a preparation method of a high-ionic-conductivity high-temperature-resistant lithium ion battery diaphragm, comprising the following steps:

[0043] Step one, preparing a spinning base film

[0044] N,N-dimethylacetamide and lithium chloride are mixed uniformly according to 100 mL:7 g to obtain an N,N-dimethylacetamide solution;

[0045] Dodecyl glycidyl ether and N,N-dimethylformamide are mixed uniformly according to 1 g:10 mL to obtain a dodecyl glycidyl ether solution;

[0046] The cellulose 20 g and the 2 mol / L sodium hydroxide solution 80 mL are weighed and added to a reaction bottle for stirring and mixing, the temperature of the reaction bottle is increased to 50 DEG C, and the system is stirred until dissolved, the dodecyl glycidyl ether solution 40 g is added to the reaction bottle, the reaction is kept for 60 min, the temperature of the reaction bottle is reduced to room temperature, the anhydrous ethanol 500 mL is added to the reaction bottle, and the filter cake is washed with anhydrous ethanol for 3 times and then dried, the filter cake is transferred to a drying box with a temperature of 60 DEG C, and dried to constant weight to obtain the modified cellulose;

[0047] Polyphthalamide, modified cellulose, N, N-dimethylacetamide solution is added to the reaction bottle according to 1g: 0.1g: 9mL, stirring and mixing, the temperature of the reaction bottle is raised to 75 DEG C, stirring until the system is dissolved, standing and degassing, to obtain the spinning solution;

[0048] The spinning solution is electrospun by electrospinning, the electrospinning environment humidity is set to 10%, the temperature is 30 DEG C, the propelling speed of the spinning solution is 1mL / h, the receiving distance is 13cm, the spinning voltage is 15kV, after spinning, the spinning base film is transferred to purified water with a temperature of 60 DEG C, soaked for 30min, washed with purified water for 3 times and then drained, and then transferred to a drying box with a temperature of 60 DEG C, dried to constant weight, to obtain a spinning base film with a thickness of 29um.

[0049] Step two, preparation of modified spinning base film

[0050] Take: melamine 5g and N, N-dimethylformamide 150mL are added to the reaction bottle and stirred and mixed, the temperature of the reaction bottle is raised to 55 DEG C, stirring until the system is dissolved, 3-isocyanate propyl trimethoxysilane 23g is added to the reaction bottle, and the reaction is kept for 50min, 0.3mol / L hydrochloric acid 50mL is added to the reaction system, and stirring is carried out for 10min, to obtain the modified liquid;

[0051] According to the solid-liquid ratio of 1:7, the spinning base film is completely immersed in the modified liquid, kept completely immersed for 40min, the spinning base film is taken out from the modified liquid, washed with purified water until neutral, then drained, the spinning base film is transferred to a drying box with a temperature of 70 DEG C, dried to constant weight, to obtain the modified spinning base film.

[0052] Step three, preparation of coating liquid

[0053] Take: boehmite 25g, mica powder 15g and purified water 250mL are added to the reaction bottle and stirred and mixed, stirring at room temperature for 4h, KH-560 3g is added to the reaction bottle, stirring for 10min, then transferred to a high pressure homogenizer, the homogenization pressure of the high pressure homogenizer is set to 130MPa, the homogenization times is 10 times, homogenization mixing, 5g of adhesive lithiumated polyacrylic acid is added to the homogenized solution, stirring and mixing for 30min, to obtain the coating liquid.

[0054] Step four, preparation of battery separator

[0055] The coating liquid is uniformly coated on both sides of the modified spinning base film according to the single side coating amount of 20mL / m 2 After uniform coating, it is transferred to a drying box with a temperature of 80 DEG C and dried to constant weight, to obtain the battery separator crude product;

[0056] The battery separator crude product is added to a roller press, the roller pressing temperature is set to 65℃, and the battery separator is compacted by roller pressing to obtain a battery separator with a thickness of 26μm.

[0057] Example 2

[0058] The present embodiment provides a preparation method of a high-ionic-conductivity high-temperature-resistant lithium-ion battery separator, comprising the following steps:

[0059] Step one, preparation of a spinning base film

[0060] N,N-dimethylacetamide and lithium chloride are mixed uniformly at 100mL:7g to obtain an N,N-dimethylacetamide solution;

[0061] Dodecyl glycidyl ether and N,N-dimethylformamide are mixed uniformly at 1g:10mL to obtain a dodecyl glycidyl ether solution;

[0062] Cellulose 22g and 2.5mol / L sodium hydroxide solution 100mL are weighed and added to a reaction bottle for stirring and mixing, the temperature of the reaction bottle is raised to 55℃, and stirring is performed until the system is dissolved, dodecyl glycidyl ether solution 46g is added to the reaction bottle, and the reaction is kept for 70min, the temperature of the reaction bottle is reduced to room temperature, 500mL of anhydrous ethanol is added to the reaction bottle, and the filter cake is washed with anhydrous ethanol for 3 times and then dried, the filter cake is transferred to a drying box with a temperature of 65℃, and dried to constant weight to obtain modified cellulose;

[0063] Polyphthalamide, modified cellulose, and N,N-dimethylacetamide solution are added to a reaction bottle for stirring and mixing, the temperature of the reaction bottle is raised to 80℃, and stirring is performed until the system is dissolved, and the spinning solution is obtained by standing and degassing;

[0064] The spinning solution is electrospun, the electrospinning environment humidity is set to 20%, the temperature is set to 35℃, the pushing speed of the spinning solution is 1mL / h, the receiving distance is 14cm, the spinning voltage is 15kV, after spinning is completed, the spinning base film is transferred to purified water with a temperature of 65℃, soaked for 40min, washed with purified water for 3 times and then drained, and then transferred to a drying box with a temperature of 65℃, and dried to constant weight to obtain a spinning base film with a thickness of 30μm.

[0065] Step two, preparation of a modified spinning base film

[0066] Weighing: melamine 5 g and N,N-dimethylformamide 150 mL are added to the reaction bottle and stirred to mix, the temperature of the reaction bottle is raised to 60 DEG C, and stirring is continued until the system is dissolved, 3-isocyanate propyl trimethoxysilane 23 g is added to the reaction bottle, and the reaction is kept at 60 DEG C for 55 min, 50 mL of 0.45 mol / L hydrochloric acid is added to the reaction system, and stirring is continued for 13 min to obtain a modified liquid;

[0067] According to the solid-liquid ratio of 1:7.5, the spinning base film is completely immersed in the modified liquid, and kept immersed for 50 min, the spinning base film is taken out from the modified liquid, washed to neutral with purified water, and then drained, the spinning base film is transferred to a drying box with a temperature of 75 DEG C, and dried to constant weight to obtain a modified spinning base film.

[0068] Step three, preparing a coating liquid

[0069] Weighing: boehmite 27 g, mica powder 17 g and purified water 250 mL are added to the reaction bottle and stirred to mix, stirring is continued at room temperature for 5 h, 3.5 g of KH-560 is added to the reaction bottle, and stirring is continued for 15 min, then it is transferred to a high-pressure homogenizer, the homogenization pressure of the high-pressure homogenizer is set to 140 MPa, and the homogenization frequency is 10 times, the homogenization mixture is obtained, 5.5 g of adhesive lithium polyacrylate is added to the homogenization solution, and stirring is continued for 40 min to obtain a coating liquid.

[0070] Step four, preparing a battery separator

[0071] The coating liquid is uniformly coated on both sides of the modified spinning base film at a single-sided coating amount of 25 mL / m 2 After uniform coating on both sides of the modified spinning base film, it is transferred to a drying box with a temperature of 83 DEG C and dried to constant weight to obtain a battery separator crude product;

[0072] The battery separator crude product is added to a roller press, the roller pressing temperature is set to 70 DEG C, and the battery separator with a thickness of 27 mu is obtained by roller pressing and compaction.

[0073] Example 3

[0074] The present embodiment provides a preparation method of a high-ionic-conductivity high-temperature-resistant lithium-ion battery separator, comprising the following steps:

[0075] Step one, preparing a spinning base film

[0076] N,N-dimethylacetamide and lithium chloride are mixed uniformly at 100 mL:7 g to obtain an N,N-dimethylacetamide solution;

[0077] Dodecyl glycidyl ether and N,N-dimethylformamide are mixed uniformly at 1 g:10 mL to obtain a dodecyl glycidyl ether solution;

[0078] Take: cellulose 24 g and 3 mol / L sodium hydroxide solution 120 mL into the reaction bottle, stir and mix, the temperature of the reaction bottle is raised to 60℃, stir until the system is dissolved, add dodecyl glycidyl ether solution 52 g to the reaction bottle, keep the reaction for 80 min, the temperature of the reaction bottle is reduced to room temperature, add anhydrous ethanol 500 mL to the reaction bottle, filter, the filter cake is washed with anhydrous ethanol for 3 times and then dried, the filter cake is transferred to a drying box with a temperature of 70℃, and dried to constant weight to obtain modified cellulose;

[0079] Add polyphthalamide, modified cellulose, and N,N-dimethylacetamide solution to the reaction bottle according to 1 g:0.1 g:9 mL, stir and mix, raise the temperature of the reaction bottle to 85℃, stir until the system is dissolved, and stand to degas, to obtain a spinning solution;

[0080] Electrospinning is used to electrospin the spinning solution, the electrospinning environment humidity is set to 30%, the temperature is 40℃, the pushing speed of the spinning solution is 1 mL / h, the receiving distance is 15 cm, the spinning voltage is 15 kV, after spinning, the spinning base film is transferred to purified water with a temperature of 70℃, soaked for 50 min, washed with purified water for 3 times and then drained, and then transferred to a drying box with a temperature of 70℃, dried to constant weight to obtain a spinning base film with a thickness of 31 μm.

[0081] Step two, preparation of modified spinning base film

[0082] Take: melamine 5 g and N,N-dimethylformamide 150 mL into the reaction bottle, stir and mix, raise the temperature of the reaction bottle to 65℃, stir until the system is dissolved, add 3-isocyanate propyl trimethoxysilane 23 g to the reaction bottle, keep the reaction for 60 min, add 0.6 mol / L hydrochloric acid 50 mL to the reaction system, stir for 15 min, and obtain a modified solution;

[0083] According to the solid-liquid ratio of 1:8, immerse the spinning base film in the modified solution completely, keep it immersed completely for 60 min, take out the spinning base film from the modified solution, wash it with purified water until it is neutral, then drain, transfer the spinning base film to a drying box with a temperature of 80℃, and dry to constant weight to obtain a modified spinning base film.

[0084] Step three, preparation of coating liquid

[0085] Take: boehmite 30 g, mica powder 20 g, and purified water 250 mL into the reaction bottle, stir and mix at room temperature for 6 h, add KH-560 4 g to the reaction bottle, stir for 20 min, then transfer it to a high-pressure homogenizer, set the homogenization pressure of the high-pressure homogenizer to 150 MPa, and homogenize for 10 times, add adhesive lithiumated polyacrylic acid 6 g to the homogenized solution, stir and mix for 50 min, and obtain a coating liquid.

[0086] Step four, preparation of battery separator

[0087] The coating liquid was coated on one side of the modified spinning base film at a single side coating amount of 30 mL / m 2 After uniform coating on both sides of the modified spinning base film, it was transferred to a drying oven at a temperature of 85℃ for drying to constant weight to prepare a battery separator crude product;

[0088] The battery separator crude product was added to the roll press, and the roll pressing temperature was set to 75℃, and the roll pressing was compacted to obtain a battery separator with a thickness of 28μm.

[0089] Comparative Example 1

[0090] The difference between this comparative example and Example 3 is that in Step one, cellulose is used instead of modified cellulose to prepare the spinning solution.

[0091] Comparative Example 2

[0092] The difference between this comparative example and Example 3 is that Step two is cancelled, and the spinning base film in Step one is used instead of the modified spinning base film in Step four.

[0093] Comparative Example 3

[0094] The difference between this comparative example and Example 3 is that in Step three, KH-560 is not added.

[0095] Performance test:

[0096] The tensile strength (longitudinal tensile strength of dry two-way stretching), thermal shrinkage (200℃, 1h), puncture strength (dry two-way stretching), and ionic conductivity of the battery separator samples prepared in Examples 1-3 and Comparative Examples 1-3 were determined according to the standard GB / T 36363-2018 "Polyolefin separator for lithium ion battery";

[0097] The specific test results are shown in Table 1 below.

[0098] Table 1-Performance test data table of samples

[0099]

[0100] Data analysis:

[0101] Comparative analysis of the data in Table 1, the battery separator prepared by the application longitudinal tensile strength reaches 197.8MPa, the heat shrinkage at 200℃ is reduced to 2.01%, the puncture strength reaches 0.182N / um, the ionic conductivity reaches 1.68mS / cm, the performance test data are better than the comparative example, which shows that, by using polyphthalic amide and modified cellulose as raw materials for electrospinning, then modifying it with triazine, and then coating with inorganic coating liquid, the mechanical strength and heat resistance of the battery separator are effectively improved, and the ionic conductivity is also improved, thereby improving the charge and discharge efficiency of the lithium battery.

[0102] The above is only an example and description of the structure of the application, and those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, as long as they do not deviate from the structure of the application or exceed the scope defined by the claims, which shall be within the protection scope of the application.

[0103] In the description of the present specification, the description of the terms "one embodiment", "example", "specific example" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are contained in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0104] The preferred embodiments of the application disclosed above are only used to help explain the application. The preferred embodiments do not describe all the details and limit the application to the specific embodiments. Obviously, many modifications and changes can be made according to the content of the present specification. The present specification selects and describes these embodiments in order to better explain the principles and practical applications of the application, so that those skilled in the art can well understand and utilize the application. The application is limited by the claims and their entire scope and equivalents.

Claims

1. A method for preparing a high ionic conductivity, high temperature resistant lithium-ion battery separator, characterized in that, The method comprises the following steps: S1, dissolving polyphthalic amide and modified cellulose into N,N-dimethylacetamide solution to form a spinning solution, and then electrospinning to obtain a spinning base film with a thickness of 29-31 mu m; S2, immersing the spinning base film into a modification liquid to modify the spinning base film, and forming a triazine modified intermediate layer on the spinning base film to obtain a modified spinning base film; S3, coating an inorganic material composed coating liquid on both sides of the modified spinning base film, and then solidifying and rolling to obtain a battery separator; The preparation method of the modified cellulose comprises the following steps: adding cellulose and lye into a reaction system and stirring to mix, increasing the temperature of the reaction system to 50-60 DEG C, stirring until the system is dissolved, adding dodecyl glycidyl ether solution into the reaction system, keeping the reaction for 60-80 min, and post-treatment to obtain the modified cellulose; The preparation method of the modified spinning base film comprises the following steps: mixing melamine and N,N-dimethylformamide, increasing the temperature of the reaction system to 55-65 DEG C, stirring until the system is dissolved, adding 3-isocyanate propyl trimethoxysilane into the reaction system, keeping the reaction for 50-60 min, adding dilute acid into the reaction system, stirring for 10-15 min, and obtaining the modification liquid; immersing the spinning base film into the modification liquid, keeping the immersion for 40-60 min, and post-treatment to obtain the modified spinning base film, wherein the amount ratio of the melamine, N,N-dimethylformamide, 3-isocyanate propyl trimethoxysilane and dilute acid is 1g:30mL:4.6g:10mL, the dilute acid is 0.3-0.6mol / L hydrochloric acid, and the solid-liquid ratio of the spinning base film and the modification liquid is 1:7-8.

2. The method for preparing a high-temperature resistant lithium-ion battery separator with high ionic conductivity according to claim 1, characterized in that, Step S1, the spinning base film is processed by the following steps: A1, mixing polyphthalic amide, modified cellulose and N,N-dimethylacetamide solution, increasing the temperature of the reaction system to 75-85 DEG C, stirring until the system is dissolved, and standing to remove bubbles to obtain the spinning solution; A2, electrospinning the spinning solution to obtain a spinning base film with a thickness of 29-31 mu m.

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 polyphthalic amide, 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 DEG C, the pushing speed of the spinning solution is 1mL / h, the receiving distance is 26-28 cm, the spinning voltage is 15kV, after the spinning is completed, the spinning base film is transferred into purified water with a temperature of 60-70 DEG C, and soaked for 30-50 min, then washed with purified water for 3 times, drained, and then transferred into a drying box with a temperature of 60-70 DEG C, and dried to constant weight to obtain the spinning base film.

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 the coating liquid is that boehmite, mica powder and purified water are mixed, stirred at room temperature for 4-6 hours to obtain a mixed solution, KH-560 is added into the mixed solution and stirred for 10-20 minutes, the mixed solution is added into a high-pressure homogenizer for homogenization mixing, a binder is added into the solution and stirred and mixed for 30-50 minutes to obtain the coating liquid.

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

6. 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: coating the coating liquid to both sides of the modified spinning base film at a single side coating amount of 20-30 mL / m 2 After drying after uniform coating to both sides of the modified spinning base film, a battery separator crude product is prepared; the battery separator crude product is added to a rolling machine, the rolling temperature is set to 65-75 ℃, and rolling compaction is performed to obtain a battery separator with a thickness of 26-28 μm.

7. A high ionic conductivity, high temperature resistant lithium-ion battery separator, characterized in that, The high-ionic-conductivity high-temperature-resistant lithium ion battery diaphragm is prepared by using the preparation method of the high-ionic-conductivity high-temperature-resistant lithium ion battery diaphragm according to any one of claims 1-6.

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