A high wettability battery separator and its preparation method

Abstract

This invention relates to the field of battery separator technology, and proposes a high-wetting battery separator and its preparation method. The high-wetting battery separator includes a base film and a coating disposed on the surface of the base film. The coating comprises raw materials with the following components: water, dispersant, silane-modified alumina, binder, wetting agent, and thickener. The silane-modified alumina comprises first silane-modified alumina, second silane-modified alumina, and third silane-modified alumina in a mass ratio of 4:3:3. The first silane-modified alumina is composed of first alumina and a first silane compound; the second silane-modified alumina is composed of second alumina and a second silane compound; and the third silane-modified alumina is composed of third alumina and a third silane compound. The particle size of the first alumina is less than that of the second alumina, which is less than that of the third alumina. This technical solution solves the problems of poor wettability and low coulombic efficiency in battery separators in related technologies.

Description

Technical Field

[0001] This invention relates to the field of battery separator technology, specifically to a high wettability battery separator and its preparation method. Background Technology

[0002] Currently, due to the rapid development of electronic and wearable devices, the demand for high-performance lithium-ion batteries is increasing. The main components of a lithium-ion battery include positive electrode materials, negative electrode materials, separators, and current collectors, among which the separator and liquid organic electrolyte have the greatest impact on battery safety. Currently, commercially available separator coating materials mainly include alumina and boehmite. Improving separator characteristics by focusing on separator coating materials is an important way to improve battery safety.

[0003] Traditional separator coatings are mostly aluminum oxide coatings. Alumina is an inert ceramic with a strong hydrophobic surface. It has a large contact angle with the electrolyte (carbonate type) and poor wettability. The electrolyte is difficult to spread and penetrate, and voids are easily formed at the separator-electrolyte interface, which increases the interfacial impedance and leads to a decrease in the coulombic efficiency of the battery separator. Summary of the Invention

[0004] This invention proposes a high wettability battery separator and its preparation method, which solves the problems of poor wettability and low coulombic efficiency of battery separators in related technologies.

[0005] The technical solution of the present invention is as follows: This invention proposes a highly wettable battery separator, comprising a base film and a coating disposed on at least one surface of the base film. The coating comprises the following raw materials in parts by weight: 60-70 parts water, 5-8 parts dispersant, 20-35 parts silane-modified alumina, 2-4 parts binder, 0.1-1 part wetting agent, and 0.5-1 part thickener. The silane-modified alumina comprises a first silane-modified alumina, a second silane-modified alumina, and a third silane-modified alumina in a mass ratio of 4:3:3. The first silane-modified alumina comprises the following raw materials in parts by weight: 40 parts of first alumina and 20 parts of first silane compound; The second silane-modified alumina comprises the following raw materials in parts by weight: 40 parts of second alumina and 20 parts of second silane compound; The third silane-modified alumina comprises the following raw materials in parts by weight: 40 parts third alumina and 20 parts third silane compounds; The particle size of the first alumina is smaller than that of the second alumina, and the particle size of the second alumina is smaller than that of the third alumina; the first silane compound, the second silane compound, and the third silane compound each independently include one or two of the following: silane coupling agent KH-560 and perfluorooctyltriethoxysilane.

[0006] As a further technical solution, the base film is a PE base film.

[0007] As a further technical solution, the average particle size of the first alumina is 300 nm, the average particle size of the second alumina is 400 nm, and the average particle size of the third alumina is 500 nm.

[0008] As a further technical solution, the first silane compound, the second silane compound, and the third silane compound are all composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane.

[0009] As a further technical solution, the mass percentage of perfluorooctyltriethoxysilane in the first silane compound is lower than the mass percentage of perfluorooctyltriethoxysilane in the second silane compound, and the mass percentage of perfluorooctyltriethoxysilane in the second silane compound is lower than the mass percentage of perfluorooctyltriethoxysilane in the third silane compound.

[0010] The hydrolysis products of silane coupling agent KH-560 and perfluorooctyltriethoxysilane (containing -Si-OH groups) can simultaneously undergo dehydration condensation reaction with hydroxyl groups on the surface of alumina, and are covalently anchored on the surface of alumina through Si-O-Al bonds, forming a mixed graft layer in which perfluorooctyltriethoxysilane and silane coupling agent KH-560 groups are randomly distributed. The perfluoroalkyl group of perfluorooctyltriethoxysilane provides hydrophobic properties, while the epoxy group of silane coupling agent KH-560 provides interfacial reactivity. The inventors discovered in experiments that the mass ratio of silane coupling agent KH-560 to perfluorooctyltriethoxysilane in the silane compounds of the first, second, and third silane-modified alumina affects the coulombic efficiency of the battery separator. Furthermore, larger alumina particle sizes increase the mass percentage of perfluorooctyltriethoxysilane in the corresponding silane compounds, further improving the coulombic efficiency of the battery separator. This may be because different mass ratios of silane coupling agent KH-560 and perfluorooctyltriethoxysilane correspond to different grafting densities on alumina surfaces of different particle sizes. Larger alumina particle sizes increase the proportion of perfluorooctyltriethoxysilane in the total mass of the silane compounds, allowing the three alumina particle sizes to have appropriate grafting densities, thereby improving the coulombic efficiency of the battery separator.

[0011] As a further technical solution, the first silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:3; the second silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:4; and the third silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:5 to 7.

[0012] As a further technical solution, the first silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:3, the second silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:4, and the third silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:6.

[0013] As a further technical solution, the preparation method of the first silane-modified alumina includes the following steps: A1. Mix the first silane compound, water, and anhydrous ethanol, adjust the pH to 4-5, and hydrolyze to obtain a mixed solution; A2. After adding the first alumina to the mixed solution and mixing, centrifuge, wash and dry to obtain the first silane-modified alumina.

[0014] As a further technical solution, in step A1, the volume ratio of the first silane compound, water, and anhydrous ethanol is 2:8:90.

[0015] As a further technical solution, the preparation method of the second silane-modified alumina includes the following steps: B1. Mix the second silane compound, water, and anhydrous ethanol, adjust the pH to 4-5, and hydrolyze to obtain a mixed solution; B2. After adding the second alumina to the mixed solution and mixing, centrifuge, wash the precipitate, and dry to obtain the second silane-modified alumina.

[0016] As a further technical solution, in step B1, the volume ratio of the second silane compound, water, and anhydrous ethanol is 2:8:90.

[0017] As a further technical solution, the preparation method of the third silane-modified alumina includes the following steps: C1. Mix the third silane compound, water, and anhydrous ethanol, adjust the pH to 4-5, and hydrolyze to obtain a mixed solution; C2. After adding the third alumina to the mixed solution and mixing, centrifuge, wash and dry to obtain the third silane-modified alumina.

[0018] As a further technical solution, in step C1, the volume ratio of the third silane compound, water, and anhydrous ethanol is 2:8:90.

[0019] As a further technical solution, in steps A2, B2 and C2, the mixing is carried out at a speed of 300 rpm for 6 hours.

[0020] As a further technical solution, in steps A1, B1 and C1, the hydrolysis temperature is 30~40℃, the stirring speed during hydrolysis is 200~300r / min, and the hydrolysis time is 90min.

[0021] As a further technical solution, the adhesive includes polyacrylic acid.

[0022] As a further technical solution, the thickener includes sodium carboxymethyl cellulose.

[0023] This invention also proposes a method for preparing a high-wetting battery separator, comprising the following steps: S1. After mixing water and dispersant evenly, mixture I is obtained; S2. Add silane-modified alumina to mixture I and mix to obtain mixture II; S3. After grinding, mixture II is used to obtain mixture III; S4. Thickener, binder and wetting agent are added to mixture III in sequence and mixed to obtain coating slurry; S5. Coating slurry onto at least one surface of the base film, drying to form a coating, thereby obtaining a highly wettable battery separator.

[0024] As a further technical solution, in step S5, the thickness of the coating is 1~1.5μm.

[0025] As a further technical solution, in step S5, the drying temperature is 50~70℃ and the drying time is 0.5~3min.

[0026] As a further technical solution, the preparation method of the highly wettable battery separator is as follows: W1. Use a mixer to stir the water and dispersant at a speed of 30~40 r / min for 15 min, and then run it at a dispersion speed of 1000~2000 r / min for 10~20 min to obtain mixture I; W2. After adding silane-modified alumina to mixture I, stir at a speed of 30~40 r / min for 60 min, and then disperse at a speed of 1000~2000 r / min for 20~40 min to obtain mixture II; W3. Grind mixture II using a sand mill to obtain mixture III; W4. Using a mixer, mix mixture II, thickener, and binder at a speed of 30-40 r / min for 30 min, then disperse at a speed of 250-350 r / min for 5-10 min. Then add wetting agent and mix at a speed of 30-40 r / min for 30 min, then disperse at a speed of 250-350 r / min for 40-60 min to obtain coating slurry. W5. Place the base film on a coating machine containing the coating slurry prepared in step W4 and coat it on at least one surface of the base film. Control the coating speed to 60~100m / min to obtain a battery separator semi-finished product. W6. The battery separator semi-finished product is pulled into the drying equipment by the traction roller and dried to form a coating, thus obtaining a highly wettable battery separator.

[0027] The working principle and beneficial effects of this invention are as follows: This invention introduces silane-modified alumina as a functional additive. Compared to unmodified alumina, it significantly improves the interfacial properties of the alumina surface, achieving efficient hydrophilic modification of the alumina and effectively reducing the contact angle of the electrolyte on the separator surface, thereby significantly enhancing the wettability of the separator in the electrolyte. Furthermore, three alumina raw materials with different particle sizes are specifically selected to prepare first silane-modified alumina, second silane-modified alumina, and third silane-modified alumina, respectively. These three are then compounded and applied to the separator coating system, allowing the modified alumina of different particle sizes to form a gradient filling structure. The synergistic effect of the three improves the coulombic efficiency of the battery separator. Detailed Implementation

[0028] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0029] In the following embodiments and comparative examples: The first type of alumina has an average particle size of 300 nm; the second type of alumina has an average particle size of 400 nm; and the third type of alumina has an average particle size of 500 nm. Polyacrylic acid, solid content: 18%~22%, viscosity: 600~1000mPa·s, pH value: 6~8; Sodium carboxymethyl cellulose, when prepared into a 1% (w / w) aqueous solution, has a viscosity of 12.4 mPa·s and a pH of 7.2.

[0030] Example 1 The coating comprises the following raw materials in parts by weight: 60 parts deionized water, 5 parts sodium dodecyl sulfate, 20 parts silane-modified alumina, 2 parts polyacrylic acid, 0.1 parts acetylacetonate, and 0.5 parts sodium carboxymethyl cellulose. The silane-modified alumina consists of a first silane-modified alumina, a second silane-modified alumina, and a third silane-modified alumina in a mass ratio of 4:3:3. The method for preparing silane-modified alumina includes the following steps: A1. Mix 20 parts of the first silane compound with deionized water and anhydrous ethanol, add 0.1 mol / L acetic acid aqueous solution to adjust the pH to 4, and hydrolyze at 40℃ for 90 min with a stirring rate of 200 r / min to obtain a mixed solution. A2. Add 40 parts of the first alumina to the mixed solution and stir at 300 rpm at 90°C for 6 hours. After centrifugation, wash with anhydrous ethanol and dry under vacuum at 80°C to obtain the first silane modified alumina. The raw materials for the first silane-modified alumina contain: the volume ratio of the first silane compound, water, and anhydrous ethanol is 2:8:90; the first silane compound is the silane coupling agent KH-560; The method for preparing second silane-modified alumina includes the following steps: B1. Mix 20 parts of the second silane compound with water and anhydrous ethanol, add 0.1 mol / L acetic acid aqueous solution to adjust the pH to 4, and hydrolyze at 40℃ for 90 min with a stirring rate of 200 r / min to obtain a mixed solution. B2. Add 40 parts of second alumina to the mixed solution, stir at 300 rpm at 90°C for 6 hours, centrifuge, wash with anhydrous ethanol, and dry under vacuum at 80°C to obtain second silane-modified alumina. The raw materials for second silane-modified alumina contain second silane compounds, water, and anhydrous ethanol in a volume ratio of 2:8:90; the second silane compound is silane coupling agent KH-560. The method for preparing third silane-modified alumina includes the following steps: C1. Mix 20 parts of the trisilane compound with water and anhydrous ethanol, add 0.1 mol / L acetic acid aqueous solution to adjust the pH to 4, and hydrolyze at 40℃ for 90 min with stirring at 200 r / min to obtain a mixed solution. C2. Add 40 parts of alumina to the mixed solution, stir at 300 rpm at 90°C for 6 hours, centrifuge, wash with anhydrous ethanol, and dry under vacuum at 80°C to obtain alumina modified with silane. The raw materials for third silane-modified alumina contain third silane compounds, water, and anhydrous ethanol in a volume ratio of 2:8:90; the third silane compound is silane coupling agent KH-560. A method for preparing a highly wettable battery separator includes the following steps: S1. Using a mixer, first stir the water and sodium dodecyl sulfate at a speed of 30 r / min for 15 min, then disperse them at a speed of 1000 r / min for 20 min to obtain mixture I; S2. After adding silane-modified alumina to mixture I, stir at 30 r / min for 60 min, then disperse at 1000 r / min for 40 min to obtain mixture II; S3. Grind mixture II using a sand mill to obtain mixture III. The particle size distribution of mixture III is: D10: 0.13μm, D50: 0.3μm, D90: 0.7μm, D99: 0.95μm; S4. Using a mixer, mix mixture III, sodium carboxymethyl cellulose and polyacrylic acid at a speed of 30 r / min for 30 min, then disperse at a speed of 250 r / min for 5 min. Then add acetylacetonate and mix at a speed of 30 r / min for 30 min, then disperse at a speed of 250 r / min for 60 min to obtain the coating slurry. S5. Place the PE base film with a thickness of 7μm on a coating machine containing the coating slurry prepared in step S4 and coat it on one surface of the PE base film. Control the coating speed to 80m / min and control the coating thickness to 1μm after coating to obtain the battery separator semi-finished product. S6. The battery separator semi-finished product is pulled into the drying equipment by the traction roller and dried at 50°C for 3 minutes to form a coating and obtain a highly wettable battery separator.

[0031] Example 2 The coating comprises the following raw materials in parts by weight: 70 parts deionized water, 8 parts sodium dodecyl sulfate, 35 parts silane-modified alumina, 4 parts polyacrylic acid, 1 part acetylacetonate, and 1 part sodium carboxymethyl cellulose. The silane-modified alumina consists of a first silane-modified alumina, a second silane-modified alumina, and a third silane-modified alumina in a mass ratio of 4:3:3. The method for preparing silane-modified alumina includes the following steps: A1. Mix 20 parts of the first silane compound with deionized and anhydrous ethanol, add 0.1 mol / L acetic acid aqueous solution to adjust the pH to 5, and hydrolyze at 30℃ for 90 min with a stirring rate of 300 r / min to obtain a mixed solution. A2. Add 40 parts of the first alumina to the mixed solution and stir at 300 rpm at 90°C for 6 hours. After centrifugation, wash with anhydrous ethanol and dry under vacuum at 80°C to obtain the first silane modified alumina. The raw materials for the first silane-modified alumina contain: the volume ratio of the first silane compound, water, and anhydrous ethanol is 2:8:90; the first silane compound is the silane coupling agent KH-560; The method for preparing second silane-modified alumina includes the following steps: B1. Mix 20 parts of the second silane compound with water and anhydrous ethanol, add 0.1 mol / L acetic acid aqueous solution to adjust the pH to 5, and hydrolyze at 30℃ for 90 min with stirring at 300 r / min to obtain a mixed solution. B2. Add 40 parts of second alumina to the mixed solution, stir at 300 rpm at 90°C for 6 hours, centrifuge, wash with anhydrous ethanol, and dry under vacuum at 80°C to obtain second silane-modified alumina. The raw materials for second silane-modified alumina contain second silane compounds, water, and anhydrous ethanol in a volume ratio of 2:8:90; the second silane compound is silane coupling agent KH-560. The method for preparing third silane-modified alumina includes the following steps: C1. Mix 20 parts of the trisilane compound with water and anhydrous ethanol, add 0.1 mol / L acetic acid aqueous solution to adjust the pH to 5, and hydrolyze at 30℃ for 90 min with stirring at 300 r / min to obtain a mixed solution. C2. Add 40 parts of alumina to the mixed solution, stir at 300 rpm at 90°C for 6 hours, centrifuge, wash with anhydrous ethanol, and dry under vacuum at 80°C to obtain alumina modified with silane. The raw materials for third silane-modified alumina contain third silane compounds, water, and anhydrous ethanol in a volume ratio of 2:8:90; the third silane compound is silane coupling agent KH-560. A method for preparing a highly wettable battery separator includes the following steps: S1. Using a mixer, first stir the water and sodium dodecyl sulfate at a speed of 40 r / min for 15 min, then disperse them at a speed of 2000 r / min for 10 min to obtain mixture I; S2. After adding silane-modified alumina to mixture I, stir at 40 r / min for 60 min, then disperse at 2000 r / min for 20 min to obtain mixture II; S3. Grind mixture II using a sand mill to obtain mixture III. The particle size distribution of mixture III is: D10: 0.13μm, D50: 0.3μm, D90: 0.70μm, D99: 0.95μm; S4. Using a mixer, mix mixture III, sodium carboxymethyl cellulose and polyacrylic acid at a speed of 40 r / min for 30 min, then disperse at a speed of 250 r / min for 10 min. Then add acetylacetonate and mix at a speed of 40 r / min for 30 min, then disperse at a speed of 350 r / min for 40 min to obtain the coating slurry. S5. Place the PE base film with a thickness of 7μm on a coating machine containing the coating slurry prepared in step S4 and coat it on one surface of the PE base film. Control the coating speed to 100m / min and control the coating thickness to 1.5μm after coating to obtain the battery separator semi-finished product. S6. The battery separator semi-finished product is pulled into the drying equipment by the traction roller and dried at 70°C for 0.5 minutes to form a coating and obtain a high wettability battery separator.

[0032] Example 3 Compared with Example 1, the only difference is that in this example, the first silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:3, the second silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:4, and the third silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:6.

[0033] Example 4 Compared with Example 1, the only difference is that in this example, the first silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:4, the second silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:3, and the third silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:6.

[0034] Example 5 Compared with Example 1, the only difference is that in this example, the first silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:3, the second silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:6, and the third silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:4.

[0035] Example 6 Compared with Example 1, the only difference is that in this example, the first silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:6, the second silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:4, and the third silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:3.

[0036] Example 7 Compared with Example 1, the only difference is that in this example, the first silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:3, the second silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:4, and the third silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:5.

[0037] Example 8 Compared with Example 1, the only difference is that in this example, the first silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:3, the second silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:4, and the third silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:7.

[0038] Example 9 Compared with Example 1, the only difference is that in this example, the first silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:4, the second silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:4, and the third silane compound is composed of silane coupling agent KH-560 and perfluorooctyltriethoxysilane in a mass ratio of 1:4.

[0039] Example 10 Compared with Example 1, the only difference is that in this example, the first silane compound, the second silane compound, and the third silane compound are all perfluorooctyltriethoxysilane.

[0040] Comparative Example 1 Compared with Example 1, the only difference is that the silane-modified alumina in this comparative example is only the first silane-modified alumina.

[0041] Comparative Example 2 Compared with Example 1, the only difference is that the silane-modified alumina in this comparative example is only the second silane-modified alumina.

[0042] Comparative Example 3 Compared with Example 1, the only difference is that the silane-modified alumina in this comparative example is only the third silane-modified alumina.

[0043] Comparative Example 4 Compared with Example 1, the only difference is that in this comparative example, the silane-modified alumina is replaced with equal amounts of first alumina, second alumina and third alumina in a mass ratio of 4:3:3.

[0044] Comparative Example 5 Compared with Example 1, the only difference is that in this comparative example, the silane-modified alumina consists of a first silane-modified alumina and a second silane-modified alumina in a mass ratio of 4:3.

[0045] Comparative Example 6 Compared with Example 1, the only difference is that the silane-modified alumina in this comparative example is composed of a second silane-modified alumina and a third silane-modified alumina in a mass ratio of 1:1.

[0046] Comparative Example 7 Compared with Example 1, the only difference is that the silane-modified alumina in this comparative example is composed of a first silane-modified alumina and a third silane-modified alumina in a mass ratio of 4:3.

[0047] Experimental Example The performance of the high wettability battery separators in Examples 1-10 and Comparative Examples 1-7 was determined using the following methods: (1) Contact angle: Sample size: Single-sided test: 5cm*5cm; Double-sided test: 10cm*10cm; Sample requirements: Smooth and flat without creases, flat surface without wrinkles and contamination; Test method: Lay the sample flat on the instrument stage, ensuring the surface is smooth and wrinkle-free; use a microsyringe to draw 2 μL of electrolyte (the electrolyte is a mixture of electrolyte and solvent, the electrolyte is lithium hexafluorophosphate (the concentration of lithium hexafluorophosphate in the electrolyte is 1 mol / L), and the solvent is composed of ethylene carbonate, dimethyl carbonate and methyl ethyl carbonate in a volume ratio of 1:1:1), and drop it 2 mm away from the diaphragm surface, forming a hanging droplet that contacts the diaphragm surface; after the droplet has settled for 5 seconds, start the instrument to capture an image of the droplet morphology; use the instrument's built-in software (Drop Shape Analysis) to calculate the contact angle value by fitting the Young-Laplace equation; test at 5 different locations on the same sample, and take the average value as the final contact angle result; (2) Coulombic efficiency: Using a membrane-packed lithium battery, the battery was placed at a constant temperature of 25°C and charged and discharged at a current density of 0.2C to test the coulombic efficiency: (a soft-pack battery with an area of ​​10cm×10cm and a thickness of 3mm), including: positive electrode, negative electrode, separator and electrolyte. The positive electrode includes: positive current collector (foamed nickel) and positive electrode coating loaded on the positive current collector (the positive electrode material in the positive electrode coating is lithium iron phosphate). The negative electrode includes: negative current collector (copper foil) and negative electrode coating loaded on the negative current collector (the negative electrode material in the negative electrode coating is graphite). The electrolyte is a mixture of electrolyte and solvent. The electrolyte is lithium hexafluorophosphate (the concentration of lithium hexafluorophosphate in the electrolyte is 1mol / L). The solvent is composed of ethylene carbonate, dimethyl carbonate and ethyl methyl carbonate in a volume ratio of 1:1:1. The measurement results are shown in Tables 1 and 2.

[0048] Table 1. Performance test results of the high wettability battery separators in Examples 1-10 and Comparative Example 4.

[0049] As shown in Table 1, the contact angle of the battery separator in Examples 1-10 of the present invention is smaller than that in Comparative Example 4, and the coulombic efficiency is greater than that in Comparative Example 4. This indicates that the addition of silane-modified alumina in the present invention reduces the contact angle between the battery separator and the electrolyte, and improves the wettability and coulombic efficiency of the separator.

[0050] Table 2 Performance test results of high wettability battery separator

[0051] As shown in Tables 1 and 2, the coulombic efficiency of the battery separators in Examples 1-10 of the present invention is greater than that in Comparative Examples 1-7, indicating that the silane-modified alumina in the present invention is composed of first silane-modified alumina, second silane-modified alumina and third silane-modified alumina, which improves the coulombic efficiency of the battery separator.

[0052] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A high wettability battery separator, characterized by, The base film and the coating layer arranged on at least one surface of the base film, the coating layer comprises the following components by weight: 60-70 parts of water, 5-8 parts of dispersant, 20-35 parts of silane modified alumina, 2-4 parts of binder, 0.1-1 parts of wetting agent, 0.5-1 parts of thickening agent, the silane modified alumina comprises the following components by weight: 40 parts of first alumina, 20 parts of first silane compound, 40 parts of second alumina, 20 parts of second silane compound, and 40 parts of third alumina, 20 parts of third silane compound. The first silane modified alumina comprises the following components by weight: 40 parts of first alumina, 20 parts of first silane compound. The second silane modified alumina comprises the following components by weight: 40 parts of second alumina, 20 parts of second silane compound. The third silane modified alumina comprises the following components by weight: 40 parts of third alumina, 20 parts of third silane compound. The particle size of the first alumina is smaller than that of the second alumina, and the particle size of the second alumina is smaller than that of the third alumina, and the first silane compound, the second silane compound and the third silane compound each independently comprise one or two of silane coupling agent KH-560 and perfluorooctyl triethoxysilane.

2. The high-wettability battery separator of claim 1, wherein, The average particle size of the first alumina is 300 nm, the average particle size of the second alumina is 400 nm, and the average particle size of the third alumina is 500 nm.

3. The high-wettability battery separator of claim 1, wherein, The first silane compound, the second silane compound and the third silane compound are composed of silane coupling agent KH-560 and perfluorooctyl triethoxysilane.

4. The high-wettability battery separator of claim 3, wherein, The mass fraction of perfluorooctyl triethoxysilane in the first silane compound is lower than that in the second silane compound, and the mass fraction of perfluorooctyl triethoxysilane in the second silane compound is lower than that in the third silane compound.

5. The high-wettability battery separator of claim 4, wherein, The first silane compound is composed of silane coupling agent KH-560 and perfluorooctyl triethoxylsilane in a mass ratio of 1:3, the second silane compound is composed of silane coupling agent KH-560 and perfluoroocty triethoxysilane in a mass ratio of 1:4, and the third silane compound is composed of silane coupling agent KH-560 and perfluorooctyle triethoxysilane in a mass ratio of 1:5-7.

6. The high-wettability battery separator of claim 1, wherein, The preparation method of the first silane modified alumina comprises the following steps: A1, mixing the first silane compound, water and anhydrous ethanol, adjusting the pH to 4-5, hydrolyzing to obtain a mixed solution; A2, adding the first alumina to the mixed solution, mixing, centrifuging, washing and drying to obtain the first silane modified alumina.

7. The high-wettability battery separator of claim 6, wherein, In step A2, the mixing is carried out at a speed of 300 rpm for 6 hours.

8. The high-wettability battery separator of claim 1, wherein, The binder comprises polyacrylic acid.

9. A method for preparing a high wettability battery separator for use in a high wettability battery separator according to any one of claims 1 to 8, characterized in that, The method comprises the following steps: S1, mixing water and dispersant uniformly to obtain a mixture I; S2, adding the silane modified alumina to the mixture I, mixing to obtain a mixture II; S3, grinding the mixture II to obtain a mixture III; S4. Thickener, binder and wetting agent are added to mixture III in sequence and mixed to obtain coating slurry; S5. Coating slurry onto at least one surface of the base film, drying to form a coating, thereby obtaining a highly wettable battery separator.

10. The method of claim 9, wherein the high-wettability battery separator is prepared by the steps of: The thickness of the coating is 1~1.5μm.

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