Preparation method of high-heat-resistance lithium ion battery diaphragm

Abstract

The invention relates to the technical field of battery diaphragms, and provides a preparation method of a high-heat-resistance lithium ion battery diaphragm. The battery diaphragm coating is prepared from the following raw materials in parts by weight: 10 to 40 parts of yttrium oxide composite aluminum oxide, 40 to 90 parts of water, 2 to 5 parts of an adhesive, 3 to 10 parts of a thickening agent, 0.2 to 0.5 part of a dispersing agent, 0.05 to 0.1 part of a wetting agent and 0.05 to 0.5 part of a flatting agent, the yttrium oxide composite aluminum oxide is obtained by treating aluminum oxide with a yttrium salt solution and then calcining; the mass ratio of the aluminum oxide to the yttrium salt is 10: (1-8). According to the technical scheme, the problem of poor heat resistance of the lithium ion battery diaphragm in the prior art is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of battery separators, and specifically, to a preparation method of a high heat-resistant lithium-ion battery separator. Background Art

[0002] In the structure of a lithium battery, the thermal shrinkage performance of the separator plays a crucial role and has a profound impact on the overall performance and safety of the battery. Specifically, the thermal shrinkage characteristics of the lithium battery separator play a vital role in ensuring the safe operation, excellent performance, and long lifespan of the battery. For this reason, when designing and manufacturing a lithium battery, the key factor of the thermal stability of the separator must be highly emphasized and fully considered. This means that the thermal stability of the separator must be improved to ensure that the separator can still maintain stable performance under various complex working environments, thereby meeting the strict requirements of the battery for safety, performance, and lifespan, etc. Summary of the Invention

[0003] The present invention provides a preparation method of a high heat-resistant lithium-ion battery separator, which solves the problem of poor heat resistance of the lithium-ion battery separator in the related art.

[0004] The technical solution of the present invention is as follows: The present invention provides a battery separator coating, which comprises raw materials with the following parts by weight: 10-40 parts of yttrium oxide composite alumina, 40-90 parts of water, 2-5 parts of an adhesive, 3-10 parts of a thickener, 0.2-0.5 parts of a dispersant, 0.05-0.1 parts of a wetting agent, and 0.05-0.5 parts of a leveling agent; the yttrium oxide composite alumina is obtained by treating alumina with a yttrium salt solution and then calcining; the mass ratio of the alumina to the yttrium salt is 10:1-8.

[0005] As a further technical solution, the mass ratio of the alumina to the yttrium salt is 8:1-3.

[0006] As a further technical solution, the yttrium salt includes one or more of yttrium acetate, yttrium nitrate, and yttrium chloride.

[0007] As a further technical solution, the preparation method of the yttrium oxide composite alumina comprises the following steps: dissolving the yttrium salt in a solution to obtain a yttrium-containing solution, adding alumina to the yttrium-containing solution, adjusting the pH>10, and obtaining the yttrium oxide composite alumina through filtration, drying, and calcination.

[0008] As a further technical solution, the solution includes water.

[0009] As a further technical solution, the reagent for adjusting the pH is an aqueous sodium hydroxide solution.

[0010] As a further technical solution, the adhesive is an emulsion-type adhesive; the emulsion-type adhesive includes an acrylate emulsion.

[0011] In the present invention, an acrylate emulsion-type adhesive is adopted, which has high adhesiveness and high temperature resistance, low irritation, good ductility after film formation, and improves the high temperature resistance of the separator.

[0012] As a further technical solution, the acrylate emulsion includes one or more of acrylate emulsion NW-1845K, acrylate emulsion TR-407, and acrylate emulsion B-959.

[0013] As a further technical solution, when the acrylate emulsion is acrylate emulsion NW-1845K and acrylate emulsion B-959, the mass ratio of acrylate emulsion NW-1845K to acrylate emulsion B-959 is 3:2 to 5.

[0014] In the present invention, by defining that the acrylate emulsion is composed of acrylate emulsion NW-1845K and acrylate emulsion B-959, and defining the mass ratio of acrylate emulsion NW-1845K to acrylate emulsion B-959 as 3:2 to 5, the puncture resistance of the battery separator is further improved.

[0015] As a further technical solution, the thickener includes one or two of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.

[0016] In the present invention, sodium carboxymethyl cellulose and lithium carboxymethyl cellulose contain a large number of hydrophilic groups, which can interact with water molecules through hydrogen bonds in an aqueous solution to form a stable three-dimensional network structure, just like building a tight "molecular skeleton" to bind water molecules therein, thereby reducing the fluidity of the system, achieving a good thickening effect, preventing phenomena such as sagging and dripping during the coating process, and improving the coating quality and uniformity of the product.

[0017] As a further technical solution, the dispersant includes one or two of ammonium polyacrylate and polyvinyl alcohol.

[0018] In the present invention, whether ammonium polyacrylate or polyvinyl alcohol is used as the dispersant, it can significantly enhance the stability of the dispersion system. In the emulsion system, they can adsorb on the surface of emulsion particles to build a solid protective film, effectively inhibiting the aggregation and sedimentation of emulsion particles and maintaining the homogeneity and stability of the system.

[0019] As a further technical solution, the wetting agent is a polyether-modified silicone.

[0020] In the present invention, a polyether-modified silicone is used as a wetting agent. In an aqueous system, the polyether segment forms strong hydrogen bond interactions with water molecules by virtue of a large number of ether bonds and hydroxyl groups, enabling the molecules to rapidly diffuse in the system, and greatly improving the hydrophilicity of the system. Meanwhile, the siloxane main chain of the silicone part endows the molecules with an extremely low surface tension, which can rapidly reduce the surface tension of the liquid, enabling the liquid to rapidly spread on the surface of the substrate, improving the coating uniformity, and eliminating defects such as flow marks and shrinkage pores.

[0021] As a further technical solution, the leveling agent is a fluorine-modified acrylate.

[0022] In the present invention, the fluorine atoms in the fluorine-modified acrylate have extremely high electronegativity and small atomic radii, endowing the fluorine-modified acrylate with an extremely low surface tension. It can rapidly migrate to the surface of the system, significantly reduce the surface tension gradient, promote the liquid to spread rapidly and uniformly, effectively eliminate defects such as flow marks and shrinkage pores, and greatly improve the flatness and gloss of the coating film.

[0023] The present invention also provides a high heat-resistant lithium-ion battery separator, which includes a base film and a coating provided on the surface of the base film, and the coating is a battery separator coating.

[0024] The present invention also provides a preparation method of a high heat-resistant lithium-ion battery separator, which includes the following steps: after uniformly mixing the raw materials of the battery separator coating, coating them on the surface of the base film, and drying to obtain the battery separator.

[0025] As a further technical solution, the mixing is divided into three times of mixing.

[0026] As a further technical solution, after the first mixing of yttrium oxide composite alumina, a dispersant, and water, an adhesive and a thickener are added for the second mixing, and then a wetting agent and a leveling agent are added for the third mixing.

[0027] As a further technical solution, the first mixing, the second mixing, and the third mixing are all carried out by a double planetary mixer.

[0028] As a further technical solution, the self-rotation speed of the first mixing is 2000 - 4000 r / min, and the revolution speed is 40 - 60 r / min; the time of the first mixing is 20 - 40 min.

[0029] As a further technical solution, the self-rotation speed of the second mixing is 2000 - 3000 r / min, and the revolution speed is 40 - 60 r / min; the time of the second mixing is 30 - 60 min.

[0030] As a further technical solution, the rotational speed of the third mixing is 2000 - 3000 r / min, and the revolution speed is 40 - 60 r / min; the time of the third mixing is 30 - 60 min.

[0031] As a further technical solution, the base film includes a polyethylene film.

[0032] As a further technical solution, the thickness of the base film is 7 - 9 μm.

[0033] As a further technical solution, the coating speed is 10 - 100 m / min.

[0034] As a further technical solution, the coating thickness is 1.5 - 3 μm.

[0035] As a further technical solution, the drying temperature is 40 - 90 °C, and the drying time is 1 - 2 min.

[0036] The working principle and beneficial effects of the present invention are as follows: In the present invention, yttrium oxide - composite alumina is used as the coating. The spherical - like particles of yttrium oxide - composite alumina can reduce the porosity inside the coating through close packing, which is more conducive to forming a continuous dense structure. The low - specific - surface - area characteristic effectively reduces the van der Waals force and capillary force between particles, enabling high - dispersion stability in a weak - interaction system, avoiding the coating uniformity defects caused by agglomeration, and improving the heat resistance of the separator. Specific Embodiments

[0037] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts fall within the scope of protection of the present invention.

[0038] In the following examples and comparative examples: Polyether - modified silicone, model: WE 3220; ammonium polyacrylate, MW: 1 million; polyvinyl alcohol, model: PVA1788; fluorine - modified acrylate, model: Levaslip 839; alumina, D10 = 0.175 μm, D50 = 0.425 μm, D90 = 0.889 μm, specific surface area: 6.6 m 2 / g; sodium carboxymethyl cellulose, viscosity: 600 - 3000 mPa·s; lithium carboxymethyl cellulose, viscosity: 4685 mPa·s.

[0039] Example 1 A preparation method of a high heat-resistant lithium-ion battery separator, comprising the following steps: S1. Add 10 parts of yttrium oxide composite alumina, 0.2 part of ammonium polyacrylate, and 40 parts of water into a double planetary mixer. After stirring for 40 minutes at a rotation speed of 2000 r / min and a revolution speed of 40 r / min, add 2 parts of an emulsion adhesive and 3 parts of sodium carboxymethyl cellulose. Stir for 40 minutes at a rotation speed of 2000 r / min and a revolution speed of 40 r / min, then add 0.05 part of polyether-modified silicone and 0.05 part of fluorine-modified acrylate. Stir for 60 minutes at a rotation speed of 2000 r / min and a revolution speed of 40 r / min to obtain a slurry; S2. Load the slurry onto a coater and coat it onto a polyethylene film with a thickness of 7 μm at a coating speed of 100 m / min. The coating thickness is 2 μm, and then introduce it into a drying device and dry it at 70 °C for 1 minute to obtain a battery separator; The emulsion adhesive is acrylate emulsion NW-1845K; Preparation method of yttrium oxide composite alumina: Dissolve 2 g of yttrium nitrate in 200 mL of water, then add 20 g of alumina, add sodium hydroxide aqueous solution to adjust the pH to 10.5, stir evenly, let stand for 30 minutes, and then obtain yttrium oxide composite alumina after filtration, drying, and calcination.

[0040] Example 2 A preparation method of a high heat-resistant lithium-ion battery separator, comprising the following steps: S1. Add 25 parts of yttrium oxide composite alumina, 0.3 part of polyvinyl alcohol, and 60 parts of water into a double planetary mixer. After stirring for 30 minutes at a rotation speed of 3000 r / min and a revolution speed of 20 r / min, add 3 parts of an emulsion adhesive and 7 parts of lithium carboxymethyl cellulose. Stir for 60 minutes at a rotation speed of 2500 r / min and a revolution speed of 20 r / min, then add 0.08 part of polyether-modified silicone and 0.25 part of fluorine-modified acrylate. Stir for 40 minutes at a rotation speed of 2500 r / min and a revolution speed of 20 r / min to obtain a slurry; S2. Load the slurry onto a coater and coat it onto a polyethylene film with a thickness of 5 μm at a coating speed of 50 m / min. The coating thickness is 3 μm, and then introduce it into a drying device and dry it at 90 °C for 1 minute to obtain a separator; The emulsion adhesive is acrylate emulsion B-959; Preparation method of yttrium oxide composite alumina: Dissolve 2 g of yttrium acetate in 200 mL of water, then add 20 g of alumina, add sodium hydroxide aqueous solution to adjust the pH to 10.5, stir evenly, let stand for 30 minutes, and then obtain yttrium oxide composite alumina after filtration, drying, and calcination.

[0041] Example 3 A preparation method of a high heat-resistant lithium-ion battery separator includes the following steps: S1. Add 40 parts of yttrium oxide composite alumina, 0.5 part of ammonium polyacrylate, and 90 parts of water into a double planetary mixer. After stirring for 20 min at a rotation speed of 4000 r / min and a revolution speed of 30 r / min, add 5 parts of an emulsion adhesive and 10 parts of sodium carboxymethyl cellulose, and stir for 30 min at a rotation speed of 3000 r / min and a revolution speed of 30 r / min. Then add 0.1 part of polyether-modified silicone and 0.5 part of fluorine-modified acrylate, and stir for 30 min at a rotation speed of 3000 r / min and a revolution speed of 30 r / min to obtain a slurry; S2. Load the slurry onto a coater and coat it onto a polyethylene film with a thickness of 9 μm at a coating speed of 10 m / min. The coating thickness is 1.5 μm. Then introduce it into a drying device and dry it at 40 °C for 2 min to obtain a separator; The emulsion adhesive is acrylate emulsion TR-407; A preparation method of yttrium oxide composite alumina: Dissolve 2 g of yttrium chloride in 200 mL of water, then add 20 g of alumina, add an aqueous sodium hydroxide solution to adjust the pH to 11, stir evenly, let it stand for 30 min, and then obtain yttrium oxide composite alumina after filtration, drying, and calcination.

[0042] Example 4 This example is different from Example 2 only in that the addition amount of yttrium acetate is 16 g.

[0043] Example 5 This example is different from Example 2 only in that the addition amount of yttrium acetate is 2.5 g.

[0044] Example 6 This example is different from Example 2 only in that the addition amount of yttrium acetate is 7.5 g.

[0045] Example 7 This example is different from Example 6 only in that the emulsion adhesive is acrylate emulsion B-959.

[0046] Example 8 This example is different from Example 7 only in that the emulsion adhesive is composed of acrylate emulsion NW-1845K and acrylate emulsion B-959 with a mass ratio of 2:1.

[0047] Example 9 This example is different from Example 7 only in that the mass ratio of acrylate emulsion NW-1845K and acrylate emulsion B-959 is 1:2.

[0048] Example 10 This example is only different from Example 7 in that the mass ratio of acrylate emulsion NW-1845K to acrylate emulsion B-959 is 3:2.

[0049] Example 11 This example is only different from Example 7 in that the mass ratio of acrylate emulsion NW-1845K to acrylate emulsion B-959 is 3:5.

[0050] Example 12 This example is only different from Example 11 in that acrylate emulsion NW-1845K is replaced with an equal amount of acrylate emulsion TR-407.

[0051] Comparative Example 1 This comparative example is only different from Example 1 in that yttrium oxide composite alumina is replaced with an equal amount of alumina.

[0052] Comparative Example 2 This comparative example is only different from Example 1 in that yttrium oxide composite alumina is replaced with an equal amount of alumina and yttrium oxide with a mass ratio of 10:1.

[0053] Experimental Example 1 The lithium-ion battery separators prepared in Examples 1-6 and Comparative Examples 1-2 were tested for the shrinkage rate in the longitudinal and transverse directions of the separator at 150 °C for 1 h according to the method in GB / T 36363-2018 "Polyolefin Separators for Lithium-Ion Batteries". The test results are shown in Table 1.

[0054] Table 1 Heat resistance test results of lithium-ion battery separators

[0055] Compared with Comparative Examples 1-2, the shrinkage rate of the separators prepared in Examples 1-6 is lower than that of Comparative Examples 1-2 under the conditions of 150 °C for 1 h, indicating that adding yttrium oxide composite alumina to the separator slurry can improve the heat resistance of the separator.

[0056] Experimental Example 2 The lithium-ion battery separators prepared in Examples 6-12 were tested for puncture strength according to the method in GB / T 36363-2018 "Polyolefin Separators for Lithium-Ion Batteries". The test results are shown in Table 2.

[0057] Table 2 Puncture resistance test results of lithium-ion battery separators

[0058] Compared with Examples 6-7, the puncture strength of the lithium-ion battery separators prepared in Examples 8-11 is higher than that in Examples 6-7, indicating that the use of acrylate emulsion NW-1845K and acrylate emulsion B-959 in combination, and when the mass ratio of acrylate emulsion NW-1845K to acrylate emulsion B-959 is 3:2 to 5, can further improve the puncture resistance of the lithium-ion battery separator.

[0059] Experimental Example 3 The air permeability of the lithium-ion battery separators prepared in Examples 1-3 was tested according to the method in GB / T 36363-2018 "Polyolefin Separators for Lithium-Ion Batteries", and the areal density of the separator was tested according to the separator mass / separator surface area = areal density. The test results are shown in Table 3.

[0060] Table 3 Performance test results of lithium-ion battery separators

[0061] As can be seen from Table 3, the air permeability and areal density of the lithium-ion battery separators prepared in Examples 1-3 are relatively high, which can improve the lithium-ion migration efficiency, thereby optimizing the fast charging performance and rate discharge capacity of the battery.

[0062] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A battery separator coating, characterized in that, Raw materials comprising the following components by weight: 10-40 parts of yttrium oxide composite alumina, 40-90 parts of water, 2-5 parts of adhesive, 3-10 parts of thickener, 0.2-0.5 parts of dispersant, 0.05-0.1 parts of wetting agent, 0.05-0.5 parts of leveling agent; the yttrium oxide composite alumina is obtained by calcining alumina after being treated with a yttrium salt solution; the mass ratio of the alumina to the yttrium salt is 10:1-8.

2. The battery separator coating according to claim 1, characterized in that, The mass ratio of the alumina to the yttrium salt is 8:1-3.

3. A battery separator coating according to claim 1, characterized in that, The yttrium salt includes one or more of yttrium acetate, yttrium nitrate, and yttrium chloride.

4. A battery separator coating according to claim 1, characterized in that The preparation method of the yttrium oxide composite alumina includes the following steps: dissolving the yttrium salt in a solution to obtain a yttrium-containing solution, adding alumina to the yttrium-containing solution, adjusting the pH > 10, and obtaining the yttrium oxide composite alumina through filtration, drying, and calcination.

5. A battery separator coating according to claim 1, wherein The adhesive is an emulsion-type adhesive; the emulsion-type adhesive includes an acrylate emulsion.

6. The battery separator coating according to claim 5, characterized in that, The acrylate includes one or more of acrylate emulsion NW-1845K, acrylate emulsion TR-407, and acrylate emulsion B-959.

7. A battery separator coating according to claim 6, characterized in that, When the acrylate is acrylate NW-1845K and acrylate B-959, the mass ratio of acrylate NW-1845K to acrylate B-959 is 3:2-5.

8. A battery separator coating according to claim 1, characterized in that, The thickener includes one or two of sodium carboxymethyl cellulose and lithium carboxymethyl cellulose.

9. A high heat-resistant lithium-ion battery separator, characterized in that, It includes a base film and a coating provided on the surface of the base film, and the coating is the battery separator coating according to any one of claims 1-8.

10. The preparation method of a highly heat-resistant lithium-ion battery separator according to claim 9, characterized in that, It includes the following steps: mixing the raw materials of the battery separator coating evenly, coating them on the surface of the base film, and drying to obtain the battery separator.

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