A high-temperature resistant composite lithium battery separator slurry and its preparation method

Abstract

The present invention relates to the technical field of battery separators, and particularly relates to a high-temperature resistant composite lithium battery separator slurry and a preparation method thereof. The slurry comprises the following raw materials in parts by weight: 6-15 parts of 3wt%-4wt% sodium alginate aqueous solution, 20-46 parts of nano-scale fumed alumina, 6-11 parts of nano-scale rutile titanium dioxide, 40-60 parts of ultrapure water, 0.1-0.8 part of a dispersant, 1.4-3.2 parts of a binder, 0.1-0.2 part of a wetting agent, and 1.5-2 parts of a high-temperature resistant composite.

Description

Technical Field

[0001] The present invention relates to the technical field of battery diaphragms, and particularly relates to a high-temperature resistant composite lithium battery diaphragm slurry and a preparation method thereof. Background Art

[0002] In today's society, the development of clean energy has become a future development trend. As an important new energy industry, the safety of electric vehicles has received increasing social attention. As a power source for electric vehicles, the safety and endurance of lithium-ion batteries are key research points. As one of the key inner components of lithium-ion batteries, the performance of the diaphragm determines the interface structure and internal resistance value of the battery, thus directly affecting the capacity, cycle, and safety performance of the battery. Most diaphragms of traditional lithium-ion batteries are mainly made of polyolefins, such as polypropylene diaphragms and polyethylene diaphragms, which have properties such as high porosity, low resistance, tear resistance, acid and alkali resistance, and good elasticity. However, such diaphragms have a low melting point, especially poor heat shrinkage resistance, posing a great safety hazard to lithium-ion batteries. In order to increase the high-temperature resistance of the diaphragm, polyester-coated ceramic diaphragms, polyethylene-coated ceramic diaphragms, etc. have emerged. However, the base film of the polyester-coated ceramic diaphragm is polyester non-woven fabric, with uneven pore size distribution. Considering mechanical properties, such diaphragms are relatively thick, affecting the volume space of the battery; the polyethylene-coated ceramic diaphragm is heavy in quality, the ceramic powder is easy to fall off, and the wettability is not good. During the process of coating the ceramic layer, it will affect the porosity of the diaphragm and increase the internal resistance of the lithium battery. The present invention uses a ceramic slurry made of nano-scale gas-phase inorganic oxides (taking nano-scale gas-phase alumina as an example in the present invention) as the main material and adding a certain mass fraction of an aqueous sodium alginate solution with a concentration of 3%-4% and a certain mass fraction of nano-scale rutile titanium dioxide on the surface of the PE base film, and roller-coating it on the surface of the PE base film through a quantitative transfer coating technology to form a composite ceramic diaphragm, which can effectively improve the high-temperature resistance of the battery diaphragm, thus effectively avoiding the safety problems of the battery. Summary of the Invention

[0003] Aiming at the deficiencies of the prior art, the present invention provides a high-temperature resistant composite lithium battery diaphragm slurry and a preparation method thereof.

[0004] The present invention is realized through the following technical solutions:

[0005] A high-temperature resistant composite lithium battery diaphragm slurry, comprising the following raw materials in parts by weight: 6-15 parts of 3wt%-4wt% aqueous sodium alginate solution, 20-46 parts of nano-scale gas-phase alumina, 6-11 parts of nano-scale rutile titanium dioxide, 40-60 parts of ultrapure water, 0.1-0.8 part of dispersant, 1.4-3.2 parts of binder, 0.1-0.2 part of wetting agent, and 1.5-2 parts of high-temperature resistant composite.

[0006] Further, the particle size of the nanoscale fumed alumina is 10 - 20 nm.

[0007] Further, the particle size of the nanoscale rutile titanium dioxide is 6 - 25 nm.

[0008] Further, the raw materials for preparing the high-temperature resistant composite include the following components in parts by weight: 8 - 12 parts of 1,3-bis(aminopropyl)tetramethyldisiloxane, 2 - 3 parts of triglycidyl p-aminophenol, 3 - 5 parts of 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 3 - 5 parts of 2,2-bis(3-amino-4-hydroxyphenyl)propane.

[0009] Further, the method for preparing the high-temperature resistant composite includes the following steps:

[0010] (1) Under a nitrogen atmosphere, take 1,3-bis(aminopropyl)tetramethyldisiloxane and add it to DMF to mix evenly to obtain a mixed solution. Add triglycidyl p-aminophenol to DMF to mix evenly. Dropwise add the mixed solution at 80 °C. After the dropwise addition, continue the reaction for 4 h. Remove the solvent under reduced pressure, wash with ethanol, and dry in vacuum to obtain product A;

[0011] (2) Under a nitrogen atmosphere, add 2,2-bis(3-amino-4-hydroxyphenyl)propane to NMP, ultrasonicate at 300 W for 15 - 20 min, add 3,3',4,4'-biphenyltetracarboxylic dianhydride in four portions, with a time interval of 25 - 35 min for each addition. After the addition is completed, stir and react at room temperature for 6 - 8 h, raise the temperature to 120 °C and react for 3 - 4 h, and then raise the temperature to 180 °C and react for 6 - 8 h;

[0012] (3) After the reaction in step (2) is completed, cool to room temperature, pour it into 3 times the volume of ethanol, centrifuge at 8000 rpm for 10 - 15 min, wash the precipitate with ethanol, and dry in vacuum to obtain product B. Mix it with product A obtained in step (1) and stir at 150 - 200 rpm for 20 - 30 min to obtain the high-temperature resistant composite.

[0013] Further, in step (1), the mass concentration of 1,3-bis(aminopropyl)tetramethyldisiloxane in DMF is 20 - 40 mg / mL.

[0014] Further, in step (1), the mass concentration of triglycidyl p-aminophenol in DMF is 20 - 30 mg / mL.

[0015] Further, in step (2), the mass concentration of 2,2-bis(3-amino-4-hydroxyphenyl)propane in NMP is 60 - 80 mg / mL.

[0016] Furthermore, the present invention also provides a method for preparing the high-temperature resistant composite lithium battery separator slurry, comprising the following steps:

[0017] S1: Add 3wt%-4wt% of sodium alginate aqueous solution and nanoscale rutile titanium dioxide into ultrapure water, add a dispersant, and disperse in a double planetary mixer for 30 min to prepare a primary mixed slurry;

[0018] S2: Add nanoscale fumed alumina to the primary mixed slurry obtained in step S1, and disperse in a double planetary mixer for 35 min to obtain a uniformly dispersed semi-finished slurry;

[0019] S3: Introduce the uniformly dispersed semi-finished slurry obtained in step S2 into a vacuum mixer, add a binder, a high-temperature resistant composite, and a wetting agent, and stir at 30-35 r / min;

[0020] S4: After the stirring in step S3 is completed, perform ultrasonic treatment at 5-8 kHz for 15 min and vacuumize at -0.8 Mpa for 20 min to obtain the high-temperature resistant composite lithium battery separator slurry.

[0021] Furthermore, in steps S1 and S2, the stirring speed of the double planetary mixer is 30-90 r / min, and the dispersion speed is 2000-3000 r / min.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The present invention provides a high-temperature resistant composite lithium battery separator slurry, which uses nano-scale gaseous inorganic oxides (nano-scale gaseous aluminum oxide) as the main material, adds an aqueous sodium alginate solution with a certain mass fraction and a concentration of 3wt%-4wt%, nano-scale rutile titanium dioxide, and also adds a certain proportion of binder, high-temperature resistant composite, and wetting agent to make the slurry. The slurry is roll-coated on the surface of the PE base film through quantitative transfer coating technology to form a separator, which can effectively improve the high-temperature resistance of the battery separator and enhance the liquid absorption and retention performance of the separator, thereby increasing the service life of the battery. The present invention prepares a high-temperature resistant composite. In the raw materials for preparing the composite, 1,3-bis(aminopropyl)tetramethyldisiloxane has good thermal stability and flexibility. The silicon-oxygen bond structure in its molecular structure has a high bond energy, showing excellent heat resistance, and can effectively resist the breakage of molecular chains in a high-temperature environment. Introducing a silicon-containing group can enhance the adhesion to inorganic materials, including substrates such as metal materials, while maintaining excellent properties such as the original high heat resistance, and further stabilizing the separator; tris(2,3-epoxypropyl)-p-aminophenol contains multiple epoxy groups, which can undergo ring-opening cross-linking reactions with the amino groups of 1,3-bis(aminopropyl)tetramethyldisiloxane during the reaction process to form a stable three-dimensional network structure, enhancing the thermal stability of the material. In addition, the cross-linking reaction can generate hydroxyl groups, providing a basis for subsequent hydrogen bond cross-linking; aromatic polyimide is a type of polymer material with high temperature resistance, low temperature resistance, radiation resistance, excellent chemical stability, and good mechanical strength. In the present invention, 3,3',4,4'-biphenyltetracarboxylic dianhydride and 2,2-bis(3-amino-4-hydroxyphenyl)propane are used for polymerization reaction to form a polymer. The obtained product has a rigid benzene ring structure, further improving the high-temperature resistance of the composite. At the same time, introducing hydroxyl groups into the polymer can cross-link with the polymers of the above 1,3-bis(aminopropyl)tetramethyldisiloxane and tris(2,3-epoxypropyl)-p-aminophenol through hydrogen bonds, increasing the cross-linking density and enhancing the high-temperature resistance; in a high-temperature environment, the high-temperature resistant composite can maintain the stability of its own structure, thereby maintaining the integrity of the lithium battery separator, avoiding problems such as separator shrinkage caused by high temperature, and ensuring the normal operation of the lithium battery. The sodium alginate used in the present invention is easily soluble in water and can form a composite material with a microporous structure through cross-linking with metal lithium ions. These microporous structures have a certain adsorption effect, can improve the ability of nano-scale gaseous aluminum oxide to adhere to the surface of the PE base film, and have good hygroscopicity. The pH value of the aqueous sodium alginate solution with a concentration of 3wt%-4wt% is 6-8. In this environment, sodium alginate has extremely strong stability, can absorb the electrolyte to a greater extent, thereby improving the liquid absorption and retention ability of the separator, increasing the cycle rate of the lithium ion battery, and thus increasing the service life of the battery.Fumed alumina is a nano-scale alumina. Compared with micron-scale alumina, it has the advantages of small and uniform particle size and large bulk density. It can form a dense packed coating on the surface of the PE-based film, thereby isolating part of the heat generated inside the battery. Moreover, its bulk density is much larger than that of micron-scale alumina, and the voids between aluminas are much smaller than those of micron-scale alumina, which can further improve the rigidity of the separator. The nano-scale fumed alumina used in the present invention has a high bulk density and forms a dense packed coating on the surface of the PE-based film, thereby isolating part of the heat generated inside the battery and further improving the rigidity of the separator. Titanium dioxide can improve the heat resistance of the separator, enhance the mechanical strength of the separator and extend its service life. Rutile titanium dioxide is the most stable type among the three types of titanium dioxide, does not undergo transformation at high temperatures, has strong stability and a relatively high relative density. Nano-scale rutile titanium dioxide can fill the pores of nano-scale fumed alumina, providing stronger rigid support for the separator and making the separator not easily deformed in a high-temperature environment. The present invention combines three materials, sodium alginate, fumed alumina and rutile titanium dioxide, which can effectively improve the high-temperature resistance performance and liquid absorption and retention performance of the lithium-ion battery separator, thereby improving the safety performance and service life of the battery. Description of the Drawings

[0024] In order to more clearly illustrate the technical solutions in the present invention or the prior art, the following will briefly introduce the drawings required for use in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only those of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0025] Figure 1 It is the micro-structure of the battery separators obtained from the slurries prepared in Example 1 of the present invention and Comparative Examples 1-3; among them, A is Example 1, B is Comparative Example 1, C is Comparative Example 2, and D is Comparative Example 3;

[0026] Figure 2 It is the high-temperature resistance performance test of the separator slurries prepared in Examples 1-3 of the present invention and Comparative Example 4. Detailed Embodiments

[0027] To make the purpose, technical solutions and advantages of the present invention clearer, the following further details the present invention with specific embodiments, but the present invention is not limited to the following embodiments. It should be noted that unless otherwise specified, the chemical reagents involved in the present invention are purchased through commercial channels.

[0028] Example 1: A high-temperature resistant composite lithium battery separator slurry, comprising the following raw materials in parts by weight: 15 parts of 3wt% sodium alginate aqueous solution, 46 parts of nano-sized fumed alumina, 11 parts of nano-sized rutile titanium dioxide, 60 parts of ultrapure water, 0.8 part of dispersant, 3.2 parts of binder, 0.2 part of wetting agent, and 2 parts of high-temperature resistant composite.

[0029] The particle size of the nano-sized fumed alumina is 20 nm; the particle size of the nano-sized rutile titanium dioxide is 25 nm.

[0030] The raw materials for preparing the high-temperature resistant composite include the following components in parts by weight: 12 parts of 1,3-bis(aminopropyl)tetramethyldisiloxane, 3 parts of tris(2,3-epoxypropyl)p-aminophenol, 5 parts of 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 5 parts of 2,2-bis(3-amino-4-hydroxyphenyl)propane.

[0031] The preparation method of the high-temperature resistant composite includes the following steps:

[0032] (1) Under a nitrogen atmosphere, 12 g of 1,3-bis(aminopropyl)tetramethyldisiloxane was added to 300 mL of DMF and mixed evenly to obtain a mixed solution. 3 g of tris(2,3-epoxypropyl)p-aminophenol was added to 100 mL of DMF and mixed evenly. The mixed solution was added dropwise at 80 °C. After the addition was completed, the reaction was continued for 4 h. The solvent was removed under reduced pressure, washed with ethanol, and dried in vacuo to obtain product A;

[0033] (2) Under a nitrogen atmosphere, 5 g of 2,2-bis(3-amino-4-hydroxyphenyl)propane was added to 62.5 mL of NMP, and ultrasonicated at 300 W for 20 min. 5 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added in four portions, with a time interval of 35 min each time. After the addition was completed, the reaction was stirred at room temperature for 8 h, heated to 120 °C and reacted for 4 h, and then heated to 180 °C and reacted for 8 h;

[0034] (3) After the reaction in step (2) was completed, it was cooled to room temperature, poured into 3 times the volume of ethanol, centrifuged at 8000 rpm for 15 min, the precipitate was washed with ethanol, and dried in vacuo to obtain product B. Product B was mixed with product A obtained in step (1) and stirred at 200 rpm for 30 min to obtain the high-temperature resistant composite.

[0035] The preparation method of the high-temperature resistant composite lithium battery separator slurry includes the following steps:

[0036] S1: Add 15 g of a 3 wt% sodium alginate aqueous solution and 11 g of nanoscale rutile titanium dioxide to 60 g of ultrapure water, and add 0.8 g of a dispersant. Disperse in a double planetary mixer for 30 min to prepare a preliminary mixed slurry; the stirring speed of the double planetary mixer is 90 r / min, and the dispersion speed is 3000 r / min.

[0037] S2: Add 46 g of nanoscale fumed alumina to the preliminary mixed slurry obtained in step S1, and disperse in a double planetary mixer for 35 min to obtain a uniformly dispersed semi-finished slurry; the stirring speed of the double planetary mixer is 90 r / min, and the dispersion speed is 3000 r / min.

[0038] S3: Pour the uniformly dispersed semi-finished slurry obtained in step S2 into a vacuum mixer, add 3.2 g of a binder, 2 g of a high-temperature resistant composite, and 0.2 g of a wetting agent, and stir at 35 r / min.

[0039] S4: After the stirring in step S3 is completed, perform ultrasonic treatment at 8 kHz for 15 min and vacuumize at -0.8 Mpa for 20 min to obtain a high-temperature resistant composite lithium battery separator slurry.

[0040] Example 2: A high-temperature resistant composite lithium battery separator slurry, comprising the following raw materials in parts by weight: 6 parts of a 4 wt% sodium alginate aqueous solution, 20 parts of nanoscale fumed alumina, 6 parts of nanoscale rutile titanium dioxide, 40 parts of ultrapure water, 0.1 part of a dispersant, 1.4 parts of a binder, 0.1 part of a wetting agent, and 1.5 parts of a high-temperature resistant composite.

[0041] The particle size of the nanoscale fumed alumina is 10 nm; the particle size of the nanoscale rutile titanium dioxide is 6 nm.

[0042] The preparation raw materials of the high-temperature resistant composite include the following components in parts by weight: 8 parts of 1,3-bis(aminopropyl)tetramethyldisiloxane, 2 parts of tris(2,3-epoxypropyl)-p-aminophenol, 3 parts of 3,3',4,4'-biphenyltetracarboxylic dianhydride, and 3 parts of 2,2-bis(3-amino-4-hydroxyphenyl)propane.

[0043] The preparation method of the high-temperature resistant composite includes the following steps:

[0044] (1) Under a nitrogen atmosphere, take 8 g of 1,3-bis(aminopropyl)tetramethyldisiloxane and add it to 400 mL of DMF and mix well to obtain a mixed solution. Add 2 g of tris(2,3-epoxypropyl)-p-aminophenol to 100 mL of DMF and mix well. Dropwise add the mixed solution at 80 °C. After the dropwise addition, continue to react for 4 h. Remove the solvent under reduced pressure, wash with ethanol, and dry in vacuo to obtain product A.

[0045] (2) Under a nitrogen atmosphere, 3 g of 2,2-bis(3-amino-4-hydroxyphenyl)propane was added to 50 mL of NMP, and ultrasonicated for 15 min at 300 W. 3 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added in four portions, with a time interval of 25 min between each addition. After the addition was completed, the reaction was stirred at room temperature for 6 h, heated to 120 °C and reacted for 3 h, and then heated to 180 °C and reacted for 6 h;

[0046] (3) After the reaction in step (2) was completed, it was cooled to room temperature, poured into 3 times the volume of ethanol, centrifuged at 8000 rpm for 10 min, the precipitate was washed with ethanol, and dried in vacuo to obtain product B. Product B was mixed with product A obtained in step (1) and stirred at 150 rpm for 20 min to obtain a high-temperature resistant composite.

[0047] A preparation method of a high-temperature resistant composite lithium battery separator slurry, comprising the following steps:

[0048] S1: 6 g of a 4 wt% sodium alginate aqueous solution and 6 g of nanoscale rutile titanium dioxide were added to 40 g of ultrapure water, and 0.1 g of a dispersant was added, and dispersed in a double planetary mixer for 30 min to prepare a primary mixed slurry; the stirring speed of the double planetary mixer was 30 r / min, and the dispersion speed was 2000 r / min;

[0049] S2: 20 g of nanoscale fumed alumina was added to the primary mixed slurry obtained in step S1, and dispersed in a double planetary mixer for 35 min to obtain a uniformly dispersed semi-finished slurry; the stirring speed of the double planetary mixer was 30 r / min, and the dispersion speed was 2000 r / min;

[0050] S3: The uniformly dispersed semi-finished slurry obtained in step S2 was introduced into a vacuum mixer, 1.4 g of a binder, 1.5 g of a high-temperature resistant composite and 0.1 g of a wetting agent were added, and stirred at 30 r / min;

[0051] S4: After the stirring in step S3 was completed, ultrasonicated at 5 kHz for 15 min and evacuated at -0.8 Mpa for 20 min to obtain a high-temperature resistant composite lithium battery separator slurry.

[0052] Example 3: A high-temperature resistant composite lithium battery separator slurry, comprising the following raw materials in parts by weight: 10 parts of a 3.5 wt% sodium alginate aqueous solution, 30 parts of nanoscale fumed alumina, 8 parts of nanoscale rutile titanium dioxide, 50 parts of ultrapure water, 0.5 part of a dispersant, 2 parts of a binder, 0.15 part of a wetting agent, and 1.8 parts of a high-temperature resistant composite.

[0053] The particle size of the nanoscale fumed alumina is 15 nm; the particle size of the nanoscale rutile titanium dioxide is 20 nm.

[0054] The raw materials for preparing the high-temperature resistant composite include the following components in parts by weight: 1,3-bis(aminopropyl)tetramethyldisiloxane 10 parts, triglycidyl p-aminophenol 2.5 parts, 3,3’,4,4’-biphenyltetracarboxylic dianhydride 4 parts, 2,2-bis(3-amino-4-hydroxyphenyl)propane 4 parts.

[0055] The method for preparing the high-temperature resistant composite includes the following steps:

[0056] (1) Under a nitrogen atmosphere, 10 g of 1,3-bis(aminopropyl)tetramethyldisiloxane was added to 300 mL of DMF and mixed evenly to obtain a mixed solution. 2.5 g of triglycidyl p-aminophenol was added to 100 mL of DMF and mixed evenly. The mixed solution was added dropwise at 80 °C. After the addition was completed, the reaction continued for 4 h. The solvent was removed under reduced pressure, washed with ethanol, and dried in vacuo to obtain product A.

[0057] (2) Under a nitrogen atmosphere, 4 g of 2,2-bis(3-amino-4-hydroxyphenyl)propane was added to 60 mL of NMP, ultrasonicated at 300 W for 18 min, and 4 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added in four portions with a time interval of 30 min between each addition. After the addition was completed, the reaction was stirred at room temperature for 7 h, heated to 120 °C and reacted for 3.5 h, and then heated to 180 °C and reacted for 7 h.

[0058] (3) After the reaction in step (2) was completed, it was cooled to room temperature, poured into 3 times the volume of ethanol, centrifuged at 8000 rpm for 12 min, the precipitate was washed with ethanol, and dried in vacuo to obtain product B. Product B was mixed with product A obtained in step (1) and stirred at 180 rpm for 25 min to obtain the high-temperature resistant composite.

[0059] The method for preparing the high-temperature resistant composite lithium battery separator slurry includes the following steps:

[0060] S1: 10 g of a 3.5 wt% sodium alginate aqueous solution and 8 g of nanoscale rutile titanium dioxide were added to 50 g of ultrapure water, and 0.5 g of a dispersant was added, and dispersed in a double planetary mixer for 30 min to prepare a primary mixed slurry; the stirring speed of the double planetary mixer was 60 r / min, and the dispersion speed was 2500 r / min.

[0061] S2: 30 g of nanoscale fumed alumina was added to the primary mixed slurry obtained in step S1, and dispersed in a double planetary mixer for 35 min to obtain a uniformly dispersed semi-finished slurry; the stirring speed of the double planetary mixer was 60 r / min, and the dispersion speed was 2500 r / min.

[0062] S3: introducing the uniformly dispersed semi-finished product slurry obtained in step S2 into a vacuum mixer, adding 2 g of a binder, 1.8 g of a high temperature resistant composite material and 0.15 g of a wetting agent, and stirring at 32 r / min;

[0063] S4: After the stirring in step S3 is completed, ultrasonic treatment is performed at 6 kHz for 15 min and vacuum is applied at -0.8 MPa for 20 min to obtain a high temperature resistant composite lithium battery separator slurry.

[0064] The only difference between Comparative Example 1 and Example 1 is that the method for preparing the high-temperature resistant composite lithium battery diaphragm slurry comprises the following steps: adding nano-gas-phase alumina to ultrapure water, adding a dispersant and dispersing it in a double planetary mixer for 30 minutes to make a semi-finished slurry, introducing it into a vacuum mixer, adding a binder, a high-temperature resistant composite and a wetting agent for stirring, performing ultrasound and vacuuming to obtain a diaphragm slurry; that is, no sodium alginate aqueous solution and nano-grade rutile titanium dioxide are added.

[0065] The only difference between Comparative Example 2 and Example 1 is that the method for preparing the high-temperature resistant composite lithium battery diaphragm slurry includes the following steps: adding nano-grade rutile titanium dioxide to ultrapure water, adding a dispersant and dispersing it in a double planetary mixer, adding nano-grade gas-phase alumina and dispersing it in a double planetary mixer, introducing it into a vacuum mixer, adding a binder, a high-temperature resistant composite and a wetting agent, stirring, ultrasonicating and vacuuming, to obtain a diaphragm slurry; that is, no sodium alginate aqueous solution is added.

[0066] The only difference between Comparative Example 3 and Example 1 is that the preparation method of the high-temperature resistant composite lithium battery diaphragm slurry comprises the following steps: adding an aqueous solution of sodium alginate to ultrapure water, adding a dispersant and dispersing it in a double planetary mixer, adding nano-grade gas-phase alumina and dispersing it in a double planetary mixer, introducing it into a vacuum mixer, adding a binder, a high-temperature resistant composite and a wetting agent, performing ultrasound and vacuuming to obtain a diaphragm slurry; that is, no nano-grade rutile titanium dioxide is added.

[0067] The only difference between Comparative Example 4 and Example 1 is that no high temperature resistant compound is added.

[0068] Experimental Example 1: The diaphragm slurry prepared in Examples 1-3 and Comparative Examples 1-3 was coated on one side or both sides of a PE diaphragm by quantitative transfer roller coating technology, and dried at 70-85°C for 2-4 min after coating. The coating machine line speed was 40-45 m / min, the thickness of the PE base film was 9 μm, and the thickness of the coating formed by coating was 1-1.8 μm. A battery diaphragm was prepared and the performance test was carried out. The results are shown in Table 1.

[0069] Table 1:

[0070]

[0071] It can be obtained from the detection data shown in Table 1 that the coating films formed by coating the diaphragm slurries prepared according to the methods of Examples 1-3 above on the surface of a 9-μm PE base film have far better anti-shrinkage ability at high temperatures than Comparative Examples 1-3. The thermal shrinkage at 150 °C for 1 h is within 0.2%, and the thermal shrinkage at 180 °C for 1 h is within 1.3%. For the coating films prepared in Comparative Examples 1-3, the thermal shrinkage rate at 150 °C for 1 h can be greater than 10%, and the thermal shrinkage at 180 °C for 1 h can be greater than 15%. The liquid absorption rates of the groups of Examples 1-3 are all greater than 100%, and the liquid retention rates are greater than 115%. For Comparative Examples 1-3, both the liquid absorption rate and the liquid retention rate are only about 60%. The liquid absorption and retention ability of the battery diaphragms prepared in Examples 1-3 is about twice that of the diaphragms in Comparative Examples 1-3. The amount of electrolyte absorbed per unit volume is relatively high, and the ionic conductivity of the battery is also relatively high, and the charge-discharge performance of the battery is better. In addition, the greater the air permeability, the greater the internal resistance of the diaphragm. A smaller air permeability value means a smaller internal resistance and a faster charge-discharge speed. Therefore, the charge-discharge performance of the batteries in the groups of Examples 1-3 is better.

[0072] Experimental Example 2: According to the method of Experimental Example 1, the diaphragm slurries prepared in Example 1 and Comparative Examples 1-3 were roll-coated to form diaphragms, and the microstructures were observed under a scanning electron microscope. The results are as Figure 1 shown.

[0073] Figure 1 The results show that the diaphragm of Example 1 is relatively dense, can isolate part of the heat generated inside the battery, improve the rigidity of the diaphragm, has a relatively high relative density, strong stability, a low porosity, and the pores of the nano-scale gas-phase alumina are filled, providing stronger rigid support for the diaphragm, so that the diaphragm is not easily deformed in a high-temperature environment.

[0074] Experimental Example 3: According to the method of Experimental Example 1, the diaphragm slurries prepared in Examples 1-3 and Comparative Example 4 were roll-coated to form diaphragms, and the breakdown temperature was measured. The results are as Figure 2 shown.

[0075] Figure 2 The results show that the high-temperature resistance of the groups of Examples 1-3 is better than that of Comparative Example 4. Comparative Example 4 does not add a high-temperature resistant composite, and the high-temperature resistance performance decreases. The high-temperature resistant composite of the present invention is formed by physically blending a polymer containing a silicon-oxygen bond and a polyimide containing a benzene ring to form an interpenetrating network structure. The high bond energy of the silicon-oxygen bond and the benzene ring structure of the polyimide effectively improve the thermal stability. The two form an interfacial interlock through hydrogen bonds, enhancing the high-temperature resistance performance.

[0076] Those of ordinary skill in the art should understand that any discussion of the above embodiments is merely exemplary and is not intended to imply that the scope of the present invention is limited to these examples; under the concept of the present invention, the technical features in the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations in different aspects of the present invention as described above, which are not provided in detail for the sake of brevity.

Claims

1. A high-temperature resistant composite lithium battery separator slurry, characterized in that, It includes raw materials in the following weight parts: 6 - 15 parts of 3wt% - 4wt% sodium alginate aqueous solution, 20 - 46 parts of nanoscale fumed alumina, 6 - 11 parts of nanoscale rutile titanium dioxide, 40 - 60 parts of ultrapure water, 0.1 - 0.8 parts of dispersant, 1.4 - 3.2 parts of binder, 0.1 - 0.2 parts of wetting agent, and 1.5 - 2 parts of high-temperature resistant composite; The particle size of the nanoscale fumed alumina is 10 - 20 nm; the particle size of the nanoscale rutile titanium dioxide is 6 - 25 nm; The raw materials for preparing the high-temperature resistant composite include the following components in weight parts: 8 - 12 parts of 1,3 - bis(aminopropyl)tetramethyldisiloxane, 2 - 3 parts of triglycidyl p-aminophenol, 3 - 5 parts of 3,3’,4,4’-biphenyltetracarboxylic dianhydride, and 3 - 5 parts of 2,2-bis(3-amino-4-hydroxyphenyl)propane; The preparation method of the high-temperature resistant composite includes the following steps: (1) Under a nitrogen atmosphere, take 1,3 - bis(aminopropyl)tetramethyldisiloxane and add it to DMF to mix evenly to obtain a mixed solution. Add triglycidyl p-aminophenol to DMF and mix evenly. Heat up and dropwise add the mixed solution. After the dropping is completed, continue the reaction. Remove the solvent under reduced pressure, wash, and dry to obtain product A; (2) Under a nitrogen atmosphere, add 2,2-bis(3-amino-4-hydroxyphenyl)propane to NMP, ultrasonicate, and add 3,3',4,4'-biphenyltetracarboxylic dianhydride in batches. After the addition is completed, stir and react at room temperature, and then heat up and react; (3) After the reaction in step (2) is completed, cool to room temperature, pour it into ethanol, centrifuge, wash the precipitate, and dry to obtain product B. Mix it with product A obtained in step (1) and stir to obtain the high-temperature resistant composite.

2. The high-temperature resistant composite lithium battery separator slurry according to claim 1, wherein, In step (1), the mass concentration of 1,3 - bis(aminopropyl)tetramethyldisiloxane in DMF is 20 - 40 mg / mL.

3. The high-temperature resistant composite lithium battery separator slurry according to claim 2, characterized in that In step (1), the mass concentration of triglycidyl p-aminophenol in DMF is 20 - 30 mg / mL.

4. The high-temperature resistant composite lithium battery separator slurry according to claim 3, wherein In step (2), the mass concentration of 2,2-bis(3-amino-4-hydroxyphenyl)propane in NMP is 60 - 80 mg / mL.

5. A method for preparing a high-temperature resistant composite lithium battery separator slurry as described in any one of claims 1-4, characterized in that, It includes the following steps: S1: Add 3wt% - 4wt% sodium alginate aqueous solution and nanoscale rutile titanium dioxide to ultrapure water, and add a dispersant. Disperse in a double planetary mixer to make a preliminary mixed slurry; S2: Add nanoscale fumed alumina to the preliminary mixed slurry obtained in step S1, and disperse in a double planetary mixer to obtain a uniformly dispersed semi-finished slurry; S3: Import the uniformly dispersed semi-finished slurry obtained in step S2 into a vacuum mixer, add a binder, a high-temperature resistant composite, and a wetting agent, and stir; S4: After the stirring in step S3 is completed, ultrasonicate and evacuate to obtain a high-temperature resistant composite lithium battery separator slurry.

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