High-temperature-resistant composite lithium battery diaphragm slurry and preparation method thereof

Abstract

The invention relates to the technical field of battery diaphragms, in particular to high-temperature-resistant composite lithium battery diaphragm slurry and a preparation method thereof. The slurry is prepared from the following raw materials in parts by weight: 6 to 15 parts of a sodium alginate aqueous solution with the concentration of 3 to 4 weight percent, 20 to 46 parts of nanoscale gas-phase aluminum oxide, 6 to 11 parts of nanoscale rutile titanium dioxide, 40 to 60 parts of ultrapure water, 0.1 to 0.8 part of a dispersing agent, 1.4 to 3.2 parts of a binding agent, 0.1 to 0.2 part of a wetting agent and 1.5 to 2 parts of a high-temperature-resistant compound.

Description

Technical Field

[0001] 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. 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 the power source of electric vehicles, the safety and endurance of lithium-ion batteries are the key research points. As one of the key inner components of lithium-ion batteries, the performance of the separator determines the interface structure and internal resistance value of the battery, thus directly affecting the capacity, cycle life, and safety performance of the battery. Most of the separators of traditional lithium-ion batteries are mainly made of polyolefins, such as polypropylene separators and polyethylene separators, which have properties such as high porosity, low resistance, tear resistance, acid and alkali resistance, and good elasticity. However, such separators 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 separator, currently, there are polyester-coated ceramic separators, polyethylene-coated ceramic separators, etc. However, the base film of the polyester-coated ceramic separator is polyester non-woven fabric, with uneven pore size distribution. Considering the mechanical properties, the thickness of such separators is relatively thick, affecting the volume space of the battery. The polyethylene-coated ceramic separator has a heavy mass, the ceramic powder is easy to fall off, and the wettability is poor. During the process of coating the ceramic layer, it will affect the porosity of the separator and increase the internal resistance of the lithium battery. The present invention uses a ceramic slurry made of nano-scale gaseous inorganic oxides (taking nano-scale gaseous aluminum oxide 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-coats it on the surface of the PE base film through a quantitative transfer coating technology to form a composite ceramic separator, which can effectively improve the high-temperature resistance of the battery separator, thereby 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 separator slurry and a preparation method thereof.

[0004] The present invention is realized through the following technical solutions: A high-temperature resistant composite lithium battery separator 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 gaseous aluminum oxide, 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.

[0005] Further, the particle size of the nano-scale gaseous aluminum oxide is 10-20 nm.

[0006] Further, the particle size of the nanoscale rutile titanium dioxide is 6 - 25 nm.

[0007] 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.

[0008] Further, the method for preparing 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. 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 vacuum to obtain product A; (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, then 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; (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.

[0009] Further, in step (1), the mass concentration of 1,3-bis(aminopropyl)tetramethyldisiloxane in DMF is 20 - 40 mg / mL.

[0010] Further, in step (1), the mass concentration of triglycidyl p-aminophenol in DMF is 20 - 30 mg / mL.

[0011] Further, in step (2), the mass concentration of 2,2-bis(3-amino-4-hydroxyphenyl)propane in NMP is 60 - 80 mg / mL.

[0012] Further, the present invention also provides a method for preparing the high-temperature resistant composite lithium battery separator slurry, including the following steps: S1: Add an aqueous solution of sodium alginate at 3 wt% - 4 wt% 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; 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 semi-finished slurry with uniform dispersion; S3: Pour the semi-finished slurry with uniform dispersion 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; 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 a high-temperature resistant composite lithium battery separator slurry.

[0013] 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.

[0014] Compared with the prior art, the present invention has the following beneficial effects: 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 concentration of 3wt%-4wt% and nano-scale rutile titanium dioxide in a certain mass fraction, 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. Among the preparation raw materials of this 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 molecular chain breakage 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 stabilize 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] 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.

[0016] Figure 1 It is the microscopic structure of the battery separators obtained from the slurries prepared in Example 1 of the present invention and Comparative Examples 1-3; wherein, A is Example 1, B is Comparative Example 1, C is Comparative Example 2, and D is Comparative Example 3; 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 DESCRIPTION OF THE EMBODIMENTS

[0017] To make the objectives, technical solutions and advantages of the present invention more clearly understood, the following further details the present invention with reference to specific embodiments. However, 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.

[0018] 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.

[0019] 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.

[0020] 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-glycidyl-p-aminophenol, 5 parts of 3,3’,4,4’-biphenyltetracarboxylic dianhydride, and 5 parts of 2,2-bis(3-amino-4-hydroxyphenyl)propane.

[0021] The preparation method of the high-temperature resistant composite includes the following steps: (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-glycidyl-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; (2) Under a nitrogen atmosphere, 5 g of 2,2-bis(3-amino-4-hydroxyphenyl)propane was added to 62.5 mL of NMP, ultrasonicated at 300W for 20 min, and 5 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added in four portions at intervals of 35 min. After the addition was completed, the reaction was stirred at room temperature for 8 h, heated to 120 °C for 4 h, and then heated to 180 °C for 8 h; (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.

[0022] The preparation method of the high-temperature resistant composite lithium battery separator slurry includes the following steps: S1: 15 g of 3wt% sodium alginate aqueous solution and 11 g of nano-sized rutile titanium dioxide were added to 60 g of ultrapure water, and 0.8 g of dispersant was added. The mixture was dispersed in a double planetary mixer for 30 min to form a primary mixed slurry; the stirring speed of the double planetary mixer was 90 r / min, and the dispersion speed was 3000 r / min; S2: Add 46 g of nano-sized fumed alumina to the primary mixed slurry obtained in step S1, and disperse it in a double planetary mixer for 35 min to obtain a semi-finished slurry with uniform dispersion. The stirring speed of the double planetary mixer is 90 r / min, and the dispersion speed is 3000 r / min; S3: Pour the semi-finished slurry with uniform dispersion obtained in step S2 into a vacuum mixer, add 3.2 g of binder, 2 g of high-temperature resistant composite, and 0.2 g of wetting agent, and stir at 35 r / min; 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.

[0023] Example 2: A high-temperature resistant composite lithium battery separator slurry, comprising the following raw materials in parts by weight: 6 parts of 4wt% sodium alginate aqueous solution, 20 parts of nano-sized fumed alumina, 6 parts of nano-sized rutile titanium dioxide, 40 parts of ultrapure water, 0.1 part of dispersant, 1.4 parts of binder, 0.1 part of wetting agent, and 1.5 parts of high-temperature resistant composite.

[0024] The particle size of the nano-sized fumed alumina is 10 nm; the particle size of the nano-sized rutile titanium dioxide is 6 nm.

[0025] The raw materials for preparing 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.

[0026] The preparation method of the high-temperature resistant composite includes the following steps: (1) Under a nitrogen atmosphere, take 8 g of 1,3-bis(aminopropyl)tetramethyldisiloxane and add it to 400 mL of DMF to mix evenly to obtain a mixed solution. Add 2 g of tris(2,3-epoxypropyl)p-aminophenol to 100 mL of DMF to mix evenly, and dropwise add the mixed solution at 80°C. After the dropping is completed, continue to react for 4 h, remove the solvent under reduced pressure, wash with ethanol, and dry in vacuum to obtain product A; (2) Under a nitrogen atmosphere, add 3 g of 2,2-bis(3-amino-4-hydroxyphenyl)propane to 50 mL of NMP, perform ultrasonic treatment at 300 W for 15 min, add 3 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride in four portions, with a time interval of 25 min for each addition. After the addition is completed, stir and react at room temperature for 6 h, raise the temperature to 120°C and react for 3 h, and then raise the temperature to 180°C and react for 6 h; (3) After the reaction in step (2) is completed, cool it to room temperature, pour it into ethanol with a volume three times that of the reaction mixture, centrifuge at 8000 rpm for 10 min, wash the precipitate with ethanol, and dry it under vacuum to obtain product B. Mix product B with product A obtained in step (1) and stir at 150 rpm for 20 min to obtain a high-temperature resistant composite.

[0027] Preparation method of a high-temperature resistant composite lithium battery separator slurry, comprising the following steps: S1: Add 6 g of a 4 wt% sodium alginate aqueous solution and 6 g of nanoscale rutile titanium dioxide to 40 g of ultrapure water, and add 0.1 g of a dispersant. Disperse in a double planetary mixer for 30 min to prepare a primary mixed slurry; the stirring speed of the double planetary mixer is 30 r / min, and the dispersion speed is 2000 r / min; S2: Add 20 g of 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; the stirring speed of the double planetary mixer is 30 r / min, and the dispersion speed is 2000 r / min; S3: Pour the uniformly dispersed semi-finished slurry obtained in step S2 into a vacuum mixer, add 1.4 g of a binder, 1.5 g of a high-temperature resistant composite, and 0.1 g of a wetting agent, and stir at 30 r / min; S4: After the stirring in step S3 is completed, perform ultrasonic treatment at 5 kHz for 15 min and vacuumize at -0.8 Mpa for 20 min to obtain a high-temperature resistant composite lithium battery separator slurry.

[0028] 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.

[0029] The particle size of the nanoscale fumed alumina is 15 nm; the particle size of the nanoscale rutile titanium dioxide is 20 nm.

[0030] The raw materials for preparing the high-temperature resistant composite include the following components in parts by weight: 10 parts of 1,3-bis(aminopropyl)tetramethyldisiloxane, 2.5 parts of tris(2,3-epoxypropyl)aminophenol, 4 parts of 3,3’,4,4’-biphenyltetracarboxylic dianhydride, and 4 parts of 2,2-bis(3-amino-4-hydroxyphenyl)propane.

[0031] Preparation method of the high-temperature resistant composite, comprising the following steps: (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 was continued for 4 h. The solvent was removed under reduced pressure, washed with ethanol, and dried in vacuo to obtain product A; (2) Under a nitrogen atmosphere, 4 g of 2,2-bis(3-amino-4-hydroxyphenyl)propane was added to 60 mL of NMP, and ultrasonic treatment was carried out at 300 W for 18 min. 4 g of 3,3',4,4'-biphenyltetracarboxylic dianhydride was added in four portions, with a time interval of 30 min each time. 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; (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 a high-temperature resistant composite.

[0032] A preparation method of a high-temperature resistant composite lithium battery separator slurry, comprising the following steps: 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; 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; S3: The uniformly dispersed semi-finished slurry obtained in step S2 was introduced into a vacuum mixer, 2 g of a binder, 1.8 g of a high-temperature resistant composite and 0.15 g of a wetting agent were added, and stirred at 32 r / min; S4: After the stirring in step S3 was completed, ultrasonic treatment was carried out at 6 kHz for 15 min, and vacuum pumping was carried out at -0.8 Mpa for 20 min to obtain a high-temperature resistant composite lithium battery separator slurry.

[0033] The difference between Comparative Example 1 and Example 1 is only that the preparation method of the high-temperature resistant composite lithium battery separator slurry comprises the following steps: adding nano-aerosil into ultrapure water, adding a dispersant and dispersing in a double planetary mixer for 30 min to prepare a semi-finished slurry, introducing it into a vacuum mixer, adding a binder, a high-temperature resistant composite and a wetting agent and stirring, and performing ultrasonic treatment and vacuum pumping to obtain the separator slurry; that is, sodium alginate aqueous solution and nano rutile titanium dioxide are not added.

[0034] The difference between Comparative Example 2 and Example 1 is only that the preparation method of the high-temperature resistant composite lithium battery separator slurry comprises the following steps: adding nano rutile titanium dioxide into ultrapure water, adding a dispersant and dispersing in a double planetary mixer, adding nano-aerosil and dispersing in a double planetary mixer, introducing it into a vacuum mixer, adding a binder, a high-temperature resistant composite and a wetting agent and stirring, performing ultrasonic treatment and vacuum pumping to obtain the separator slurry; that is, sodium alginate aqueous solution is not added.

[0035] The difference between Comparative Example 3 and Example 1 is only that the preparation method of the high-temperature resistant composite lithium battery separator slurry comprises the following steps: adding sodium alginate aqueous solution into ultrapure water, adding a dispersant and dispersing in a double planetary mixer, adding nano-aerosil and dispersing in a double planetary mixer, introducing it into a vacuum mixer, adding a binder, a high-temperature resistant composite and a wetting agent, performing ultrasonic treatment and vacuum pumping to obtain the separator slurry; that is, nano rutile titanium dioxide is not added.

[0036] The difference between Comparative Example 4 and Example 1 is only that the high-temperature resistant composite is not added.

[0037] Experimental Example 1: The separator slurries prepared in Examples 1-3 and Comparative Examples 1-3 were coated on a PE separator on one or both sides by a quantitative transfer roll coating technique, dried at 70-85 °C for 2-4 min after coating, the line speed of the coater 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. The battery separators were prepared and subjected to performance tests, and the results are shown in Table 1.

[0038] Table 1:

[0039] It can be seen from the detection data shown in Table 1 that the coating films formed by coating the separator 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, the liquid absorption rates and liquid retention rates are only about 60%. The liquid absorption and retention abilities of the battery separators prepared in Examples 1-3 are about twice those of the separators in Comparative Examples 1-3. The amount of electrolyte absorbed per unit volume is relatively high, 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 separator. 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.

[0040] Experimental Example 2: According to the method of Experimental Example 1, the separator slurries prepared in Example 1 and Comparative Examples 1-3 were roll-coated to form separators, and the microstructures were observed under a scanning electron microscope. The results are as Figure 1 shown.

[0041] Figure 1 The results show that the separator of Example 1 is relatively dense, can isolate part of the heat generated inside the battery, improve the rigidity of the separator, has a relatively high relative density, strong stability, a low porosity, and the pores of nano-scale gas-phase alumina are filled, providing stronger rigid support for the separator, making the separator not easily deformed in a high-temperature environment.

[0042] Experimental Example 3: According to the method of Experimental Example 1, the separator slurries prepared in Examples 1-3 and Comparative Example 4 were roll-coated to form separators, and the film-breaking temperatures were measured. The results are as Figure 2 shown.

[0043] Figure 2 The results show that the high-temperature resistance performance 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.

[0044] Those of ordinary skill in the art should understand that the discussion of any of the above embodiments is only 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: The raw materials include the following parts by weight: 6-15 parts of 3wt%-4wt% sodium alginate aqueous solution, 20-46 parts of nano-grade fumed alumina, 6-11 parts of nano-grade 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 compound; The particle size of the nano-scale fumed alumina is 10-20 nm; the particle size of the nano-scale rutile titanium dioxide is 6-25 nm; 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; The method for preparing the high temperature resistant composite comprises the following steps: (1) Under a nitrogen atmosphere, 1,3-bis(aminopropyl)tetramethyldisiloxane is added to DMF and mixed to obtain a mixed solution, triglycidyl-p-aminophenol is added to DMF and mixed to obtain a mixed solution, the mixed solution is added dropwise at a higher temperature, and the reaction is continued after the addition is completed, the solvent is removed under reduced pressure, the product is washed, and the product is dried to obtain a product A; (2) Under nitrogen atmosphere, 2,2-bis(3-amino-4-hydroxyphenyl)propane was added to NMP, and 3,3',4,4'-biphenyltetracarboxylic dianhydride was added in batches. After the addition was completed, the reaction was stirred at room temperature, and then the temperature was raised to react; (3) After the reaction in step (2) is completed, the mixture is cooled to room temperature, poured into ethanol, centrifuged, the precipitate is washed, and dried to obtain product B, which is mixed with product A obtained in step (1) and stirred to obtain a high temperature resistant composite.

2. The high temperature resistant composite lithium battery separator slurry according to claim 1, characterized in that: 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, characterized in that: In step (2), the mass concentration of the 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 according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1: adding 3wt%-4wt% sodium alginate aqueous solution and nano-grade rutile titanium dioxide into ultrapure water, and adding a dispersant, and dispersing in a double planetary mixer to form a primary mixed slurry; S2: adding nano-sized fumed alumina to the primary mixed slurry obtained in step S1, and dispersing the mixture in a double planetary mixer to obtain a uniformly dispersed semi-finished slurry; S3: introducing the uniformly dispersed semi-finished product slurry obtained in step S2 into a vacuum mixer, adding a binder, a high temperature resistant composite material and a wetting agent, and stirring; S4: After the stirring in step S3 is completed, ultrasonication and vacuumization are performed to obtain a high temperature resistant composite lithium battery separator slurry.

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