Battery separator with high heat-resistant ceramic coating layer and manufacturing method thereof

Abstract

The present invention provides a battery separator with a high heat-resistant ceramic coating layer, the battery separator including a base film and a ceramic coating layer applied thereon, the ceramic coating layer including a ceramic powder and an adhesive, the adhesive bonding the ceramic powder to the base film, and the ceramic powder further having a density of 5 to 15 g / cm 3 The present invention is characterized by including at least one inorganic substance A, which is a high-density inorganic substance. The beneficial effects of the present invention are as follows: When a ceramic coating layer containing at least one high-density inorganic substance A is coated on a base film, the inorganic substance A has a high gravity, so it can act as a "pillar" in the three-dimensional structure of the separator, forming a more stable and rigid structure, which can resist large-area shrinkage caused by stress release due to the movement of molecular chains inside the separator in a high-temperature environment.

Description

[Technical Field]

[0001] The present invention relates to the technical field of battery manufacturing, and more particularly to a battery separator with a high-temperature resistant ceramic coating layer for improving the electrochemical performance and safety of lithium batteries, and a method for manufacturing the same. [Background technology]

[0002] With the widespread use of power batteries and energy storage batteries in our daily lives, their safety is receiving increasing attention. Separators, a key component that affects battery safety, are facing increasing safety requirements and expectations. Battery companies both in China and abroad are being asked to ensure separators maintain dimensional stability even at temperatures ranging from 220 to 300°C.

[0003] Currently, the heat resistance of separators is improved mainly by coating alumina or boehmite on microporous polyolefin membranes. However, with the increasing demand for heat resistance in high-power, high-energy density electronic products, such separators are no longer able to meet market demands. Therefore, there is an urgent need to develop high-temperature resistant separators that exhibit high-temperature stability, for example, even at temperatures of 220°C. Summary of the Invention [Problem to be solved by the invention]

[0004] The present invention aims to solve the problem of high-temperature thermal stability of separators. While conventional production techniques lack heat resistance and are prone to safety issues, the present invention can achieve the thermal stability of separators and improve safety. Specifically, the base film has internal stress due to tensile stretching during the production process, and the stress is released by the movement of molecular chains inside the separator in a high-temperature environment, resulting in large-area shrinkage. Another object of the present invention is to provide a method for manufacturing a battery separator with a high-temperature resistant ceramic coating layer. [Means for solving the problem]

[0005] In order to achieve the above object, the present invention provides a ceramic coating layer comprising a base film and a ceramic coating layer applied thereon, the ceramic coating layer comprising ceramic powder and an adhesive, the adhesive bonding the ceramic powder to the base film, and the ceramic powder further having a density of 5 to 15 g / cm. 3 The present invention provides a battery separator with a highly heat-resistant ceramic coating layer, which comprises at least one inorganic substance A represented by the formula (I).

[0006] Preferably, the ceramic powder further has an average density of 1 to 15 g / cm 3 The density is 0.1 to 5 g / cm 3 The density of the inorganic substance A is higher than the density of the inorganic particles.

[0007] Preferably, the inorganic particles comprise titanium oxide, aluminum hydroxide, magnesium hydroxide, aluminum oxide, boehmite, magnesium oxide, calcium oxide, beryllium oxide, or any combination thereof.

[0008] Preferably, the inorganic material A comprises barium titanate, cerium oxide, zirconia, yttrium oxide, or any combination thereof.

[0009] Preferably, the ceramic coating layers are applied to one or both sides of the base film, and the ratio of ceramic powder to adhesive contained in each ceramic coating layer is the same or different.

[0010] Preferably, the ceramic powder has a D50 particle size of 0.05 μm to 2 μm and a specific surface area of ​​1 to 200 m 2 / g.

[0011] Preferably, the inorganic substance A has a particle size of 0.05 μm to 2 μm and a specific surface area of ​​1 to 200 m 2 / g.

[0012] Preferably, the mass ratio of the inorganic substance A to the ceramic powder is 1:(1 to 100).

[0013] A method for manufacturing a battery separator with a high heat resistant ceramic coating layer, comprising: Step S1: adding a dispersant to deionized water and stirring thoroughly until homogeneous to obtain a dispersant solution; Step S2: adding a ceramic powder containing at least one inorganic substance A to the dispersant solution and continuing to stir, and then adding it to a mill to be dispersed; Step S3: Add a thickener, an adhesive, and a wetting agent to the milled mixture in step S2, stir the mixture uniformly, and then demagnetize and filter the mixture to obtain a coating slurry. The method is characterized by including step S4 of applying the coating slurry obtained in step S3 to a base film, and then drying it in an oven to obtain a separator with a coating layer.

[0014] Preferably, the mass ratio of the inorganic substance A to the ceramic powder is 1:(1 to 100).

[0015] Preferably, the ceramic powder has a D50 particle size of 0.05 μm to 2 μm, and the particle size of the inorganic substance A is 0.05 μm to 2 μm. [Effects of the Invention]

[0016] The present invention provides a battery separator with a high-temperature-resistant ceramic coating layer and a manufacturing method thereof, which have the following beneficial effects: The ceramic material is distributed throughout the three-dimensional structure of the separator, forming a specific rigid skeleton, which provides rigid support and effectively prevents the separator from shrinking or melting under thermal runaway conditions. When a ceramic coating layer containing at least one high-density inorganic substance A is applied to a base film, its high gravity acts as a "pillar" in the three-dimensional structure of the separator, forming a more stable and rigid structure, thereby resisting large-area shrinkage caused by stress release due to the movement of molecular chains inside the separator under high-temperature conditions. [Brief explanation of the drawings]

[0017] [Figure 1] 2 is a schematic diagram illustrating the morphology of the ceramic coating layer and base film after exposure to high temperatures. FIG. [Figure 2] 1 is a flowchart illustrating a manufacturing flow of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0018] In order to make the above and / or other objects, advantages and features of the present invention more comprehensible, preferred embodiments of the present invention will be described in detail below.

[0019] Referring to FIG. 1, the present invention provides a ceramic coating layer (1) comprising a base film (2) and a ceramic coating layer (1), the ceramic coating layer (1) comprising ceramic powder (12) and an adhesive, the adhesive bonding the ceramic powder (12) to the base film (2), and the ceramic powder (12) further comprising a ceramic powder having a density of 5 to 15 g / cm. 3 The present invention provides a battery separator with a high heat-resistant ceramic coating layer, which contains at least one inorganic substance A(11) of the formula:

[0020] In some embodiments, the inorganic material A (11) comprises barium titanate, cerium oxide, zirconia, yttrium oxide, or any combination thereof, and has a particle size of 0.05 μm to 2 μm, preferably 0.1 to 1 μm, and a density of 5 to 15 g / cm. 3 and preferably, the density is 5 to 10 g / cm 3 The specific surface area is 1 to 200 m 2 / g, preferably 1 to 100m 2 / g.

[0021] In some embodiments, the ceramic powder (12) further comprises a ceramic powder (12) having an average density of 1 to 15 g / cm. 3 The density is 0.1 to 5 g / cm 3The density of the inorganic substance A is higher than the density of the inorganic particles.

[0022] In some embodiments, the inorganic particles include titanium oxide, aluminum hydroxide, magnesium hydroxide, aluminum oxide, boehmite, magnesium oxide, calcium oxide, beryllium oxide, or any combination thereof. The total mass ratio of the ceramic powder (12) to deionized water is 1:(1.25-10), i.e., 10%-80%, the D50 particle size of the ceramic powder (12) is 0.05 μm-2 μm, preferably 0.1-1 μm, and the average density of the ceramic powder (12) is 1-15 g / cm. 3 , preferably 2 to 10 g / cm 3 The average specific surface area of ​​the ceramic powder (12) is 1 to 200 m 2 / g, preferably 1 to 100m 2 / g.

[0023] In some embodiments, the ceramic coating layers (1) are applied to one or both sides of the base film (2), and the ratio of ceramic powder (12) to adhesive contained in each ceramic coating layer (1) may be the same or different.

[0024] In some embodiments, the base film (2) used comprises a polyethylene microporous film, a polypropylene microporous film, or a polypropylene / polyethylene composite microporous film, and the base film (2) has a thickness of 3 to 20 μm, preferably 5 to 14 μm, and an air permeability of 30 to 300 s / 100 cc.

[0025] In some embodiments, the thickness of the coating layer is 0.5 μm to 7 μm, preferably 0.5 to 4 μm.

[0026] In some embodiments, the total mass ratio of inorganic substance A (11) to ceramic powder (12) is 1:(1-100), i.e., inorganic substance A (11) accounts for 1%-100%, preferably 50%-100%, of the mass of ceramic powder (12). Manufacturing method

[0027] A method for manufacturing a battery separator having a high heat-resistant ceramic coating layer (1), comprising: a step S1 of adding a dispersant to deionized water and stirring the mixture until the mixture is homogeneous to obtain a dispersant solution; Density 5-15g / cm 3 Step S2: adding a ceramic powder (12) containing at least one inorganic substance A (11) to the dispersant solution and stirring continuously, and then adding it to a mill to disperse it; Step S3: Add a thickener, an adhesive, and a wetting agent to the milled mixture in step S2, stir uniformly, and then demagnetize and filter the mixture to obtain a coating slurry. The method includes step S4 in which the coating slurry obtained in step S3 is applied to the base film (2), followed by oven drying to obtain a separator with a coating layer, and a wire bar, gravure roll, etc. are used for the coating.

[0028] In some embodiments, in step S1, the dispersant is at least one of polyethylene glycol, sodium polyacrylate, polypropylene, polyethylene, polyvinylpyrrolidone, ammonium polyacrylate, and sodium hexametaphosphate, and the total mass ratio of the dispersant to the ceramic powder (12) is 1:(50-2000).

[0029] In some embodiments, in step S2, the ceramic powder (12) is further selected so that the average density of the ceramic powder (12) is 1 to 15 g / cm 3 , preferably 2 to 10 g / cm 3 The density is 0.5 to 15 g / cm 3 The density of the inorganic substance A is higher than the density of the inorganic particles.

[0030] In some embodiments, in step S3, the adhesive comprises polyvinylidene fluoride, polytetrafluoroethylene, polyvinyl alcohol, polyacrylic acid, polyacrylonitrile and polyacrylic acid ester, polyacrylamide, melamine, styrene butadiene rubber, phosphates, silicates, lignin, polyimide, or any combination thereof, and the total mass ratio of the adhesive to the ceramic powder (12) is 1:(5-100).

[0031] In some embodiments, in step S3, the thickener comprises sodium carboxymethylcellulose, methylcellulose, hydroxypropylmethylcellulose, cardo resin, or any combination thereof, and the total mass ratio of the thickener to the ceramic powder (12) is (0.1-2):100.

[0032] In some embodiments, in step S3, the wetting agent includes an organically modified silicone-based agent, a polyol-based agent, an aliphatic alcohol ether-based agent, or any combination thereof, and the ratio of the total mass of the wetting agent to the ceramic powder (12) is (0.01-2):100.

[0033] In some embodiments, in step S4, the coating method is one of gravure printing, doctor blade coating, extrusion coating, or wire bar coating, and the coating position is on one or both sides of the base film (2).

[0034] In some embodiments, in step S4, the base film (2) coated with the coating slurry is dried. The drying method is preferably oven drying. The drying temperature is 40 to 150°C, and the drying time is 0.01 to 0.5 hours.

[0035] The methods for producing slurries provided in the present application can all be carried out at room temperature, are easy to operate, and are easy to scale up. Example 1

[0036] A method for manufacturing a battery separator with a high heat-resistant ceramic coating layer is as follows.

[0037] Step 1: Weigh out 0.5 g of sodium polyacrylate and dissolve it in 100 g of deionized water. Stir using a cantilever stirrer at 1000 r / min for 1 h to form an aqueous dispersion solution.

[0038] Step 2: 10 g of barium titanate (density 6 g / cm 3 , specific surface area 3.4m 2 / g) was added to the dispersant solution and stirred at 2000 r / min for 1 h using a cantilever stirrer, and then 90 g of alumina (density 4 g / cm 3 , specific surface area 7.5m 2 / g) is added to an aqueous dispersant solution, and the mixture is stirred at 2000 r / min for 1 hour using a cantilever stirrer, and then milled.

[0039] Step 3: Add 3 g of sodium carboxymethylcellulose aqueous solution and stir for 30 minutes. Then add 10 g of acrylate emulsion and stir using a cantilever stirrer at 300 r / min for 1 hour to obtain a uniform dispersion. Then add 0.05 g of silicone surface additive and stir using a cantilever stirrer at 300 r / min for 1 hour to obtain a uniform slurry.

[0040] Step 4: Use a film-forming device to coat the slurry onto one side of a 9 μm-thick polyethylene film, then dry in an oven at 60°C for 3 minutes to achieve a coating thickness of 2 μm, resulting in a separator coated on one side. Next, use a film-forming device to coat the slurry onto the other side of the polyethylene film, then dry in an oven at 60°C for 3 minutes to achieve a coating thickness of 2 μm, resulting in a separator coated on both sides with a thickness of 4 μm. Example 2

[0041] This example provides a method for manufacturing a battery separator with a high heat-resistant ceramic coating layer. The difference between Example 2 and Example 1 is that the amount of barium titanate powder added in Step 2 is 30 g, and the amount of alumina added is 70 g. Example 3

[0042] This example provides a method for manufacturing a battery separator with a high heat-resistant ceramic coating layer. The difference between Example 3 and Example 1 is that the amount of barium titanate powder added in step 2 is 50 g, and the amount of alumina added is 50 g. Example 4

[0043] This example provides a method for manufacturing a battery separator with a high heat-resistant ceramic coating layer. The difference between Example 4 and Example 1 is that the amount of barium titanate powder added in step 2 is 70 g, and the amount of alumina added is 30 g. Example 5

[0044] This example provides a method for manufacturing a battery separator with a high heat-resistant ceramic coating layer. The difference between Example 5 and Example 1 is that the amount of barium titanate powder added in step 2 is 90 g, and the amount of alumina added is 10 g. Example 6

[0045] This example provides a method for manufacturing a battery separator with a high heat-resistant ceramic coating layer. The difference between Example 6 and Example 1 is that the amount of barium titanate powder added in step 2 is 100g, and the amount of alumina added is 0g. Example 7

[0046] This example provides a method for manufacturing a battery separator with a high heat-resistant ceramic coating layer. The difference between Example 7 and Example 1 is that the amount of barium titanate powder added in step 2 is 30 g, and the alumina is boehmite (density 3 g / cm 3 ) and the amount added is 70g. Comparative Example 1

[0047] To compare the effect of barium titanate in improving the heat resistance of the separator, Comparative Example 1 differs from Example 1 in that the amount of barium titanate powder added in step 2 is 0 g and the amount of alumina added is 100 g. Comparative Example 2

[0048] In order to compare the effect of barium titanate on improving the heat resistance of the separator, Comparative Example 2 differs from Example 1 in that the barium titanate powder in step 2 is replaced with boehmite, and the amount of added alumina is 30 g, and 70 g, respectively. Comparative Example 3

[0049] In order to compare the effect of barium titanate on improving the heat resistance of the separator, Comparative Example 3 differs from Example 1 in that the barium titanate powder in step 2 is replaced with boehmite, and the amount of added alumina is 50 g. Comparative Example 4

[0050] In order to compare the effect of barium titanate on improving the heat resistance of the separator, Comparative Example 4 differs from Example 1 in that the barium titanate powder in step 2 is replaced with boehmite, and the amount of added alumina is 70 g, and 30 g, respectively. Comparative Example 5

[0051] In order to compare the effect of barium titanate on improving the heat resistance of the separator, Comparative Example 5 differs from Example 1 in that the barium titanate powder in step 2 is replaced with boehmite, and the added amount is 90 g, and the added amount of alumina is 10 g. 2. Performance test

[0052] [Test for average unit surface density of coating layer] Test method: Three separators measuring 40mm x 60mm were cut from the base film and ceramic coating film. First, the three base films were weighed on an analytical balance and labeled m1, m2, and m3. Next, the thicknesses of the three base films were measured using a thickness gauge and labeled h1, h2, and h3. Similarly, the three ceramic coating films were weighed on an analytical balance and labeled m4, m5, and m6. Next, the thicknesses of the three ceramic coating films were measured using a thickness gauge and labeled h4, h5, and h6. The average areal density of the base film was calculated using the formula ρ = (m1 + m2 + m3) / 3 / 0.0024, and labeled ρ1. The average areal density of the ceramic coating film was calculated using the formula ρ = (m1 + m2 + m3) / 3 / 0.0024, and labeled ρ2. Furthermore, since the average thickness h of the coating layer is (h4 + h5 + h6) / 3 - (h1 + h2 + h3) / 3, the average unit surface density of the coating layer was finally calculated as ρ = (ρ2 - ρ1) / h.

[0053] [Heat shrinkage test] Test method: Six ceramic coating separators measuring 60mm x 40mm were cut, and two holes were punched in the MD and TD directions at the same positions on each ceramic coating. The distance between the holes in the MD direction was measured as d1, and the distance between the holes in the TD direction was measured as d2. The six coatings were divided into two groups, each placed on 10 sheets of A4 paper, and the 10 sheets of A4 paper were placed on the coating and secured with clips. One group was placed in a constant temperature oven at 150°C, and the other was placed in a constant temperature oven at 220°C for 1 hour. The distance between the holes in the MD and TD directions of the separators after heating was measured as d3 and d4, respectively. The thermal shrinkage of the separator in the MD direction (p = (d1 - d3) / d1 * 100%) and the thermal shrinkage in the TD direction (p = (d2 - d4) / d2 * 100%) were calculated.

[0054] [High temperature nail penetration test] Test method: A 50mm diameter ceramic coating film was cut and fixed to the test mold of the hot nail penetration tester with a fixing clip, ensuring the surface was as flat and the force was as uniform as possible. A 0.2mm diameter hot nail with a chamfered tapered tip was selected, the temperature was set to 250°C, the distance was set to -0.1mm, and the program was run. After the test was completed, the shape and size of the black dots or holes in the pierced separator were observed and analyzed under a digital microscope.

[0055] The performance of the coated separators produced in Examples 1 to 7 and Comparative Examples 1 to 5 was measured, and the measurement results are shown in Table 1 below. JPEG2025534198000002.jpg166170

[0056] As can be seen from Table 1 and Examples 1 to 6, as the ratio of inorganic material A to ceramic powder increases, the average unit area density of the coating layer increases, and the thermal shrinkage of the separator at 150°C and 220°C decreases, with the thermal shrinkage at 150°C being <3%. In the hot nail penetration test, the rupture diameter also decreases accordingly.

[0057] As can be seen from a comparison of the results of Examples 1 to 7 and Comparative Examples 1 to 5, the addition of inorganic substance A to the ceramic powder significantly improves the thermal shrinkage rate of the separator and reduces the diameter of the rupture caused by hot nail penetration, thereby improving the safety of the battery.

[0058] As can be seen from a comparison of the results of Example 7 and Comparative Examples 1 and 2, by adding inorganic substance A to the ceramic powder, even though the average unit area density of the coating layer of Example 7 is smaller than that of Comparative Examples 1 and 2, the thermal shrinkage rate of the separator can be significantly improved and the diameter of the rupture in hot nail penetration can be reduced, thereby improving the safety of the battery.

[0059] The above is merely a preferred embodiment of the present invention and does not limit the scope of the claims of the present invention. Therefore, any simple equivalent changes and modifications made based on the claims of the present invention and the contents of the specification belong to the scope of the claims of the present invention.

Claims

1. a base film and a ceramic coating layer applied thereon, the ceramic coating layer including a ceramic powder and an adhesive, the adhesive bonding the ceramic powder to the base film, and the ceramic powder having a density of 5 to 15 g / cm ３ 1. A battery separator with a high heat-resistant ceramic coating layer, comprising at least one inorganic substance A,

2. The ceramic powder further has an average density of 1 to 15 g / cm ３ The density is 0.1 to 5 g / cm ３ 2. The battery separator according to claim 1, wherein the density of said inorganic material A is higher than the density of said inorganic particles.

3. 3. The battery separator of claim 2, wherein said inorganic particles comprise titanium oxide, aluminum hydroxide, magnesium hydroxide, aluminum oxide, boehmite, magnesium oxide, calcium oxide, beryllium oxide, or any combination thereof.

4. 10. The battery separator of claim 1, wherein said inorganic A comprises barium titanate, cerium oxide, zirconia, yttrium oxide, or any combination thereof.

5. 2. The battery separator of claim 1, wherein the ceramic coating layers are applied to one or both sides of the base film, and the ratio of ceramic powder to adhesive contained in each ceramic coating layer is the same or different.

6. The ceramic powder has a D50 particle size of 0.05 μm to 2 μm and a specific surface area of ​​1 to 200 m ２ 10. The battery separator of claim 1, wherein the tensile strength is 0.05 to 0.15 MPa.

7. The inorganic substance A has a particle size of 0.05 μm to 2 μm and a specific surface area of ​​1 to 200 m ２ 10. The battery separator of claim 1, wherein the tensile strength is 0.05 to 0.15 MPa.

8. 2. The battery separator according to claim 1, wherein the mass ratio of the inorganic material A to the ceramic powder is 1:(1-100).

9. Step S1: adding a dispersant to deionized water and stirring thoroughly until homogeneous to obtain a dispersant solution; Density 5 to 15 g / cm ３ Step S2: adding a ceramic powder containing at least one inorganic substance A to the dispersant solution and continuing to stir, and then adding it to a mill to disperse it; Step S3: Adding a thickener, an adhesive, and a wetting agent to the milled mixture in this order and stirring uniformly. Then, demagnetizing and filtering the mixture to obtain a coating slurry. and step S4 of applying the coating slurry obtained in step S3 to a base film, and then drying the applied slurry in an oven to obtain a separator with a coating layer.

10. 10. The manufacturing method according to claim 9, wherein the mass ratio of the inorganic substance A to the ceramic powder is 1:(1 to 100).

11. 10. The manufacturing method according to claim 9, wherein the ceramic powder has a D50 particle size of 0.05 μm to 2 μm, and the inorganic substance A has a particle size of 0.05 μm to 2 μm.

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