A slurry for battery separator, its preparation method, and applications

Abstract

The present invention discloses a slurry for battery separators, a preparation method thereof, and an application. The slurry comprises the following components: 0.2 - 0.7% of a dispersant, 0.1 - 0.5% of a wetting agent, 0.15 - 0.9% of a thickening agent, 5 - 10% of a binder, 13 - 40% of a hyperbranched polyacrylamide / modified alumina composite material, and the balance being ultrapure water. In the technical solution provided by the present invention, by using the hyperbranched polyacrylamide / modified alumina composite material and modifying the surface of alumina, alumina is bonded to hyperbranched polyacrylamide through Si - O bonds, avoiding the phase separation of alumina and hyperbranched polyacrylamide materials during high-speed dispersion; while the hyperbranched polyacrylamide material retains the dispersibility of the polyacrylamide material for the alumina slurry, it exhibits excellent solubility of the hyperbranched material, improves the problem that the alumina material is not easily dispersed in water, and shortens the dispersion time of the alumina material in water.

Description

Technical Field

[0001] The present invention relates to the technical field of battery materials, and particularly relates to a slurry for battery separators, a preparation method thereof, and an application thereof. Background Art

[0002] With the continuous development of new energy technologies, energy storage batteries, as a common energy storage and release device, play an increasingly important role in production and life. With the continuous development and update of technologies, the requirements for the performance and safety of batteries are also constantly increasing. As one of the important components inside the battery, the battery separator is located between the positive and negative electrodes, playing the role of isolating and separating the positive and negative electrodes, preventing direct electron conduction between the positive and negative electrodes, and providing an ion channel, enabling ions (such as lithium ions) between the positive and negative electrodes to freely transmit, realizing the charge and discharge process of the battery, thereby preventing the occurrence of safety problems such as short circuits and battery overheating, and playing a key function in the battery.

[0003] Polyolefin separators are a commonly used type of battery separator. However, the polyolefin separators in the prior art have poor thermal stability. When the battery undergoes thermal runaway, the polyolefin separator may shrink, which may cause the direct contact between the positive and negative electrodes, leading to an exacerbation of the thermal runaway.

[0004] By modifying the surface layer of the polyolefin separator, its stability at high temperatures can be improved, and the battery thermal runaway time can be extended. Currently, the commonly used modification material is alumina. However, alumina has a relatively high Mohs hardness, which will cause wear to accessories such as the anilox roll and doctor blade of the equipment during long-term use. Alumina is prone to agglomeration and difficult to disperse in water. After long-term standing, alumina will settle in the slurry and even agglomerate again, resulting in damage to accessories such as the anilox roll and doctor blade of the equipment when using this slurry for coating. For example, Chinese Patent (CN116937067A) discloses a separator for a semi-solid battery and a preparation method thereof. The preparation method of this separator is to mix 10 - 40 wt% of a lithium salt with cellulose, then add 3 - 10 wt% of alumina and a DMSO (dimethyl sulfoxide) solution containing 2 - 5 wt% of PVDF, and uniformly coat the above-mentioned composite solid electrolyte coating solution on a polyolefin base film by means of knife coating, and obtain a composite solid electrolyte coating separator after washing with water and drying. The surface layer of the polyolefin separator of this battery is modified with alumina, which will cause problems such as wear of accessories such as the anilox roll and doctor blade of the equipment and sedimentation and agglomeration of alumina in the slurry during long-term use. Therefore, how to prepare a safe, reliable, and highly stable polyolefin separator is an urgent problem to be solved at present. Summary of the Invention

[0005] The main object of the present invention is to propose a slurry for battery separators, a preparation method thereof, and an application thereof, aiming to solve the problems that the existing alumina-modified polyolefin separators cause damage to accessories such as the anilox roll and doctor blade of the equipment, as well as sedimentation and agglomeration of alumina in the slurry.

[0006] To achieve the above object, the present invention provides a slurry for battery separator. By mass percentage, the slurry comprises the following components: 0.2 - 0.7% of dispersant, 0.1 - 0.5% of wetting agent, 0.15 - 0.9% of thickening agent, 5 - 10% of binder, 13 - 40% of hyperbranched polyacrylamide / modified alumina composite material, and the balance is ultrapure water.

[0007] Aluminum oxide-based inorganic materials have strong polarity. When coating polymer materials on their surfaces, it is easy to cause uneven coating of polymer materials on the surface of aluminum oxide due to poor compatibility between aluminum oxide and resin materials, thereby reducing the uniformity of aluminum oxide materials and the mechanical properties of polymer material / aluminum oxide composites. Even worse, phase separation may occur.

[0008] Hyperbranched polyacrylamide is a kind of polymer with good thermal stability. It can be well miscible with water and its aqueous solution has viscoelasticity. At the same time, the viscosity of the hyperbranched polyacrylamide aqueous solution is lower than that of conventional polyacrylamide. When the viscosity of the slurry is lower, it is easier to use the reverse gravure coating method to modify the surface of polyolefin separators. Hyperbranched polyacrylamide can act as a stabilizer for alumina slurry and improve the problem of easy agglomeration of alumina slurry during standing. When hyperbranched polyacrylamide is uniformly coated on the surface of aluminum oxide, it can use the elasticity of its polymer material to reduce the wear of aluminum oxide powder on equipment accessories.

[0009] Optionally, the dispersant is an ammonium salt material;

[0010] The thickening agent is sodium carboxymethyl cellulose;

[0011] The binder is an acrylic resin;

[0012] The wetting agent is a silanol-based nonionic surfactant.

[0013] Optionally, the preparation method of the hyperbranched polyacrylamide / modified alumina composite material comprises the following steps:

[0014] S1. Place aluminum oxide in a vacuum oven for drying, and then cool to obtain preliminarily treated aluminum oxide;

[0015] S2. Add ethanol and ultrapure water to a container, stir evenly, then add acetic acid to adjust the pH of the aqueous solution to 5 - 6. Add vinyltrimethoxysilane, hydrolyze, then add the preliminarily treated aluminum oxide, heat to reflux, cool down, filter, wash, and dry to obtain modified aluminum oxide;

[0016] S3. Add acrylamide and hyperbranched polyglycidyl ether into a container, then add ultrapure water and stir. Add the modified alumina, introduce an inert gas and stir. Add ammonium cerium nitrate, heat for reaction, filter, wash and dry to obtain a hyperbranched polyacrylamide / modified alumina composite material.

[0017] In the present invention, vinyltrimethoxysilane is used to modify the surface of alumina. Compared with the conventional modifier 3-aminopropyltriethoxysilane, this modifier has better hydrophobicity and can improve the dispersion performance of alumina in water. At the same time, through the modification of alumina, its surface contains Si groups, which can be combined with polymer materials through Si-O bonds to avoid phase separation of alumina and polymer materials during high-speed dispersion.

[0018] Optionally, in step S1, the drying temperature is 70 - 90 °C; the drying time is 10 - 14 h.

[0019] Optionally, in step S2, the mass ratio of vinyltrimethoxysilane to the preliminarily treated alumina is (2 - 4):(180 - 220).

[0020] Optionally, in step S2, the hydrolysis time is 40 - 80 min, the temperature for heating and refluxing is 58 - 62 °C, the time for heating and refluxing is 4.5 - 5.5 h, and ethanol solution is used for washing.

[0021] Optionally, in step S3, the mass ratio of acrylamide, hyperbranched polyglycidyl ether, modified alumina, and ammonium cerium nitrate is (80 - 120):(1 - 2):(450 - 550):(1 - 2).

[0022] Optionally, in step S3, the inert gas includes nitrogen, the temperature for heating reaction is 50 - 70 °C, the time for heating reaction is 2.5 - 3.5 h, and a mixed solution of water and ethanol is used for washing.

[0023] The present invention also provides a method for preparing a slurry for battery separator as described above, and the preparation method includes the following steps:

[0024] Add a dispersant and a hyperbranched polyacrylamide / modified alumina composite material into ultrapure water, stir and mix evenly, add a thickener and a binder, stir, and then add a wetting agent, stir and filter to obtain a slurry for battery separator.

[0025] The present invention also provides an application of the slurry for battery separator as described above in a battery.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] (1) The slurry provided by the present invention uses a hyperbranched polyacrylamide / modified alumina composite material. By modifying the surface of alumina, alumina is bonded to hyperbranched polyacrylamide through Si-O bonds, avoiding the phase separation of alumina and hyperbranched polyacrylamide materials during high-speed dispersion;

[0028] (2) In the hyperbranched polyacrylamide / modified alumina composite material, while the hyperbranched polyacrylamide material retains the dispersibility of the polyacrylamide material for alumina slurry, it exhibits the excellent solubility of hyperbranched materials, improves the problem that alumina materials are not easily dispersed in water, and shortens the dispersion time of alumina materials in water;

[0029] (3) The hyperbranched polyacrylamide / modified alumina composite material uniformly coats a layer of hyperbranched polyacrylamide material on the surface of alumina, improves the problems of increased particle size and alumina agglomeration during the static storage of alumina slurry, and extends the shelf life of alumina slurry;

[0030] (4) The hyperbranched polyacrylamide / modified alumina composite material can effectively reduce the wear of the coated slurry on the anilox roll and doctor blade of the coating equipment relying on the advantages of high elasticity and good toughness of the hyperbranched polyacrylamide material, thereby extending the service life of the anilox roll and doctor blade. Detailed implementation mode

[0031] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or instruments not specified by the manufacturer are all conventional products that can be obtained through commercial purchase. In addition, the meaning of "and / or" appearing throughout the text includes three parallel solutions. Taking "A and / or B" as an example, it includes solution A, solution B, or the solution where A and B are satisfied simultaneously. In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that those skilled in the art can achieve it. When the combination of technical solutions is contradictory or cannot be achieved, it should be considered that such a combination of technical solutions does not exist and is not within the scope of protection required by the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0032] The technical solutions of the present invention will be further described in detail below in conjunction with specific embodiments. It should be understood that the following embodiments are only used to explain the present invention and are not used to limit the present invention.

[0033] Example 1 A slurry for battery separator, comprising the following steps:

[0034] (1) Place 20 g of alumina in a vacuum oven at 80 °C and dry for 12 h, then cool to room temperature to obtain preliminarily treated alumina. Add 95 ml of ethanol and 5 ml of ultrapure water to a 250 mL three-necked round-bottom flask, stir evenly, add acetic acid to adjust the pH of the aqueous solution to 5.5, add 0.34 g of vinyltrimethoxysilane, hydrolyze for 1 h, add the preliminarily treated alumina, heat to 60 °C and reflux at a constant temperature for 5 h. After the temperature drops to room temperature, filter and wash three times with ethanol, then dry to obtain modified alumina;

[0035] (2) Add 2 g of acrylamide and 0.02 g of hyperbranched polyglycidyl ether to a 250 mL three-necked round-bottom flask, add 90 mL of ultrapure water and stir until dissolved, add 10 g of modified alumina, pass in nitrogen and stir for 30 min, add 0.02 g of ammonium cerium nitrate and heat to 60 °C, react at a constant temperature for 3 h, stop heating, filter, wash three times with a water / ethanol mixed solution, and dry to obtain a hyperbranched polyacrylamide / modified alumina composite material;

[0036] (3) Add 0.45% ammonium chloride and 15% hyperbranched polyacrylamide / modified alumina to 78% ultrapure water, stir at a speed of 700 rpm for 40 min, add 0.45% sodium carboxymethyl cellulose and 6% acrylic resin, stir at a speed of 500 rpm for 30 min, add 0.1% span 80, and stir at a speed of 400 rpm for 10 min to obtain a slurry for battery separator.

[0037] Example 2 A slurry for battery separator, comprising the following steps:

[0038] (1) Place 20 g of alumina in a vacuum oven at 70 °C and dry for 14 h, then cool to room temperature to obtain preliminarily treated alumina. Add 95 ml of ethanol and 5 ml of ultrapure water to a 250 mL three-necked round-bottom flask, stir evenly, add acetic acid to adjust the pH of the aqueous solution to 5, add 0.24 g of vinyltrimethoxysilane, hydrolyze for 1 h, add the preliminarily treated alumina, heat to 60 °C and reflux at a constant temperature for 4.5 h. After the temperature drops to room temperature, filter and wash three times with ethanol, then dry to obtain modified alumina;

[0039] (2) Add 2 g of acrylamide and 0.02 g of hyperbranched polyglycidyl ether to a 250 mL three-necked round-bottom flask, add 90 mL of ultrapure water and stir until dissolved, add 10 g of modified alumina, pass in nitrogen and stir for 30 min, add 0.02 g of ammonium cerium nitrate and heat to 50 °C, react at a constant temperature for 3.5 h, stop heating, filter, wash three times with a water / ethanol mixed solution, and dry to obtain a hyperbranched polyacrylamide / modified alumina composite material;

[0040] (3) Add 0.45% ammonium chloride and 30% hyperbranched polyacrylamide / modified alumina to 63% ultrapure water, stir at a speed of 700 rpm for 40 min, add 0.45% sodium carboxymethyl cellulose and 6% acrylic resin, stir at a speed of 500 rpm for 30 min, add 0.1% wetting agent, stir at a speed of 400 rpm for 10 min to obtain the slurry for battery separator.

[0041] Example 3 A slurry for battery separator, comprising the following steps:

[0042] (1) Place 20 g of alumina in a 90 °C vacuum oven and dry for 10 h, then cool to room temperature to obtain preliminarily treated alumina; add 95 ml of ethanol and 5 ml of ultrapure water to a 250 mL three-necked round-bottom flask, stir evenly, add acetic acid to adjust the pH of the aqueous solution to 6, add 0.40 g of vinyltrimethoxysilane, hydrolyze for 1 h, add the preliminarily treated alumina, heat to 60 °C and reflux at a constant temperature for 5.5 h, after the temperature drops to room temperature, filter and wash three times with ethanol, and dry to obtain modified alumina;

[0043] (2) Add 2 g of acrylamide and 0.02 g of hyperbranched polyglycidyl ether to a 250 mL three-necked round-bottom flask, add 90 mL of ultrapure water and stir until dissolved, add 10 g of modified alumina, introduce nitrogen and stir for 30 min, add 0.02 g of ammonium cerium nitrate, heat to 70 °C, react at a constant temperature for 2.5 h, stop heating, filter, wash three times with a water / ethanol mixed solution, and dry to obtain hyperbranched polyacrylamide / modified alumina composite;

[0044] (3) Add 0.2% ammonium chloride and 40% hyperbranched polyacrylamide / modified alumina to 53.8% ultrapure water, stir at a speed of 700 rpm for 40 min, add 0.5% sodium carboxymethyl cellulose and 5% acrylic resin, stir at a speed of 500 rpm for 30 min, add 0.5% Span 80, stir at a speed of 400 rpm for 10 min to obtain the slurry for battery separator.

[0045] Comparative Example 1 A slurry for battery separator, comprising the following steps:

[0046] (1) Place 20 g of alumina in an 80 °C vacuum oven and dry for 12 h, then cool to room temperature to obtain preliminarily treated alumina;

[0047] (2) Add 2 g of acrylamide and 0.02 g of hyperbranched polyglycidyl ether into a 250 mL three-necked round-bottom flask. Add 90 mL of ultrapure water and stir until dissolved. Add 10 g of preliminarily treated alumina, introduce nitrogen gas and stir for 30 min. Add 0.02 g of ammonium cerium nitrate and heat to 60 °C, keep the temperature constant and react for 3 h. Stop heating, filter, wash three times with a water / ethanol mixed solution, and dry to obtain a hyperbranched polyacrylamide / alumina composite material;

[0048] (3) Add 0.45% ammonium chloride and 15% hyperbranched polyacrylamide / alumina into 78% ultrapure water, with a rotation speed of 700 rpm, stir for 40 min. Add 0.45% sodium carboxymethyl cellulose and 6% acrylic resin, with a rotation speed of 500 rpm, stir for 30 min. Add 0.1% Span 80, with a rotation speed of 400 rpm, stir for 10 min to obtain a slurry for battery separator.

[0049] Comparative Example 2 A slurry for battery separator, comprising the following steps:

[0050] (1) Place 20 g of alumina in a vacuum oven at 80 °C and dry for 12 h, then cool to room temperature to obtain preliminarily treated alumina; Add 95 ml of ethanol and 5 ml of ultrapure water into a 250 mL three-necked round-bottom flask, stir evenly, add acetic acid to adjust the pH of the aqueous solution to 5.5, add 0.34 g of vinyltrimethoxysilane, hydrolyze for 1 h, add the preliminarily treated alumina, heat to 60 °C and keep the temperature constant for reflux for 5 h. After the temperature drops to room temperature, filter, wash three times with ethanol, and dry to obtain modified alumina;

[0051] (2) Add 2 g of acrylamide into a 250 mL three-necked round-bottom flask, add 90 mL of ultrapure water and stir until dissolved. Add 10 g of modified alumina, introduce nitrogen gas and stir for 30 min. Add 0.02 g of ammonium cerium nitrate and heat to 60 °C, keep the temperature constant and react for 3 h. Stop heating, filter, wash three times with a water / ethanol mixed solution, and dry to obtain a polyacrylamide / modified alumina composite material;

[0052] (3) Add 0.45% ammonium chloride and 15% polyacrylamide / modified alumina into 78% ultrapure water, with a rotation speed of 700 rpm, stir for 40 min. Add 0.45% sodium carboxymethyl cellulose and 6% acrylic resin, with a rotation speed of 500 rpm, stir for 30 min. Add 0.1% Span 80, with a rotation speed of 400 rpm, stir for 10 min to obtain a slurry for battery separator.

[0053] Comparative Example 3 A slurry for battery separator, comprising the following steps:

[0054] (1) Place 20 g of alumina in a vacuum oven at 80 °C and dry for 12 h, then cool to room temperature to obtain preliminarily treated alumina;

[0055] (2) Add 0.45% ammonium chloride and 15% alumina to 78% ultrapure water, stir at a speed of 700 rpm for 40 min, add 0.45% sodium carboxymethyl cellulose and 6% acrylic resin, stir at a speed of 500 rpm for 30 min, add 0.1% span 80, and stir at a speed of 400 rpm for 10 min to obtain the slurry for battery separator.

[0056] Application Examples 1 - 6

[0057] Uniformly roll-coat the slurries for battery separators prepared in Examples 1 - 3 and Comparative Examples 1 - 3 on both sides of a 9-μm-thick polyolefin separator, bake at 80°C and then wind up to obtain the alumina-modified composite separators for lithium-ion batteries prepared in Application Examples 1 - 6.

[0058] Test Methods and Results

[0059] Test the particle size and viscosity of the slurries for battery separators obtained in Examples 1 - 3 and Comparative Examples 1 - 3 to obtain Table 1; test the thermal shrinkage at 150°C / h and breakdown voltage of the composite separators obtained in Application Examples 1 - 3 and Application Examples 4 - 6 to obtain Table 2.

[0060] Table 1 Statistical Table of Particle Size and Viscosity of Slurries for Battery Separators

[0061]

[0062]

[0063] Table 2 Statistical Table of Thermal Shrinkage and Breakdown Voltage Data of Composite Separators

[0064]

[0065] The service life of the gravure roll in Application Example 1 is 570,000 meters, while the service life of the gravure roll in Application Example 6 is 255,000 meters.

[0066] In summary, at the same dispersion time, the particle sizes of Examples 1 to 3 are mostly smaller than those of Comparative Examples 1 to 3, indicating that the hyperbranched polyacrylamide / modified alumina composite material has better dispersion performance than alumina materials, polyacrylamide / modified alumina materials, and hyperbranched polyacrylamide / alumina materials; under the same thickness condition, the thermal shrinkage of Application Examples 1 to 3 is significantly smaller than that of Application Examples 4 to 6, indicating that the hyperbranched polyacrylamide / modified alumina slurry has more excellent thermal shrinkage performance than alumina slurry, polyacrylamide / modified alumina slurry, and hyperbranched polyacrylamide / alumina slurry; under the same thickness condition, the breakdown voltage value of Application Examples 1 to 3 is significantly greater than that of Application Examples 4 to 6, indicating that the hyperbranched polyacrylamide / alumina slurry has better voltage resistance performance than alumina slurry, polyacrylamide / modified alumina slurry, and hyperbranched polyacrylamide / alumina slurry; Application Example 1 and Application Example 6 show that the improved slurry can effectively reduce the wear of alumina slurry on equipment fittings.

[0067] The above are only the preferred embodiments of the present invention, and do not limit the patent scope of the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the patent protection scope of the present invention.

Claims

1. A slurry for battery separator, characterized in that, By mass percentage, the slurry comprises the following components: 0.2-0.7% of a dispersant, 0.1-0.5% of a wetting agent, 0.15-0.9% of a thickening agent, 5-10% of a binder, 13-40% of a hyperbranched polyacrylamide / modified alumina composite material, and the balance being ultrapure water; The preparation method of the hyperbranched polyacrylamide / modified alumina composite material comprises the following steps: S1. Place alumina in a vacuum oven for drying and then cool it to obtain preliminarily treated alumina; S2. Add ethanol and ultrapure water to a container, stir evenly, adjust the pH of the aqueous solution to 5-6 with acetic acid, add vinyltrimethoxysilane, hydrolyze, then add the preliminarily treated alumina, heat to reflux, cool down, filter, wash, and dry to obtain modified alumina; S3. Add acrylamide and hyperbranched polyglycidyl ether to a container, then add ultrapure water and stir, add the modified alumina, stir while passing in an inert gas, add ammonium cerium nitrate, heat for reaction, filter, wash, and dry to obtain a hyperbranched polyacrylamide / modified alumina composite material.

2. The slurry for battery separator according to claim 1, wherein, The dispersant is an ammonium salt material; the thickening agent is a sodium carboxymethyl cellulose type; the binder is an acrylic resin type; the wetting agent is a silanol nonionic surfactant.

3. The slurry for battery separator according to claim 1, characterized in that, In step S1, the drying temperature is 70-90 °C; the drying time is 10-14 h.

4. The slurry for battery separator according to claim 1, wherein In step S2, the mass ratio of vinyltrimethoxysilane to the preliminarily treated alumina is (2-4):(180-220).

5. The slurry for battery separator according to claim 1, characterized in that, In step S2, the hydrolysis time is 40-80 min, the temperature for heating to reflux is 58-62 °C, the time for heating to reflux is 4.5-5.5 h, and the washing is carried out with an ethanol solution.

6. The slurry for battery separator according to claim 1, characterized in that, In step S3, the mass ratio of acrylamide, hyperbranched polyglycidyl ether, modified alumina, and ammonium cerium nitrate is (80-120):(1-2):(450-550):(1-2).

7. The slurry for battery separator according to claim 1, wherein In step S3, the inert gas includes nitrogen, the temperature for the heating reaction is 50-70 °C, the time for the heating reaction is 2.5-3.5 h, and the washing is carried out with a mixed solution of water and ethanol.

8. A method for preparing a slurry for a battery separator according to any one of claims 1 to 7, characterized in that, The preparation method comprises the following steps: Add the dispersant and the hyperbranched polyacrylamide / modified alumina composite material to ultrapure water, stir and mix evenly, add the thickening agent and the binder, stir, and then add the wetting agent, stir and filter to obtain a slurry for a battery separator.

9. Application of a slurry for a battery separator according to any one of claims 1 to 7 in a battery.

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