Battery separator and preparation method, and battery

Abstract

A battery separator and a preparation method, and a battery. The battery separator comprises a base membrane, a first bonding layer, a heat-resistant layer, and a second bonding layer. The first bonding layer has a first thickness H1 μm, and has a first coverage rate C1% for the base membrane, the heat-resistant layer has a second thickness H2 μm, the second bonding layer has a third thickness H3 μm, and has a second coverage rate C2 % for the heat-resistant layer, and it is satisfied that: H2>H1+H3, C2=(0.6-1.2)*(H1+H3) / H2%, and C1=(0.1-0.3)*H2 / H1%.

Description

Battery separator, preparation method thereof, and battery

[0001] This application claims priority to the Chinese patent application filed with the China Patent Office on November 28, 2023, with application number 202311608351.6 and invention name “A battery separator and preparation method, battery, and electrical equipment”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application relates to, but is not limited to, the field of battery technology. Background Art

[0003] With the increasing adoption of new energy vehicles, the lamination process has become a rising star in lithium battery internal molding processes, owing to its advantages such as high volume utilization, high efficiency, stable structure, low internal resistance, and long cycle life. In the thermal lamination process, the battery's negative electrode and separator are pressed together at a certain temperature to form a single unit, which is then integrated with the positive electrode. This method significantly increases production speed by combining electrode die-cutting and lamination, streamlining production steps and significantly improving efficiency. Technical Solutions

[0004] In the first aspect, the present application provides a battery separator, comprising: a base film; a first adhesive layer located on one side of the base film, the first adhesive layer having a first thickness H1 μm, and the first adhesive layer having a first coverage C1% of the base film; a heat-resistant layer located on a side of the base film away from the first adhesive layer, the heat-resistant layer having a second thickness H2 μm; a second adhesive layer located on a side of the heat-resistant layer away from the base film, the second adhesive layer having a third thickness H3 μm, and the second adhesive layer having a second coverage C2% of the heat-resistant layer; satisfying: H2>H1+H3, C2=(0.6~1.2)*(H1+H3) / H2%, and C1=(0.1~0.3)*H2 / H1%.

[0005] Optionally, the first thickness H1 of the first adhesive layer is 0.5 μm to 1.5 μm.

[0006] Optionally, the second thickness H2 of the heat-resistant layer is 1.5 μm to 3 μm.

[0007] Optionally, a third thickness H3 of the second adhesive layer is 0.5 μm to 1 μm.

[0008] Optionally, the first coverage C1 is 30-50%.

[0009] Optionally, the second coverage C2 is 40-60%.

[0010] Optionally, the material of the first adhesive layer includes polyvinylidene fluoride.

[0011] Optionally, the material of the heat-resistant layer includes bimetallic oxide and fibrous polyimide.

[0012] Optionally, the material of the second adhesive layer includes non-fluorine-based polyacrylate.

[0013] Optionally, the primary particle size of the polyvinylidene fluoride is 100 nm to 300 nm.

[0014] Optionally, the mass ratio of the bimetallic oxide to the fibrous polyimide is (1.3-3):1.

[0015] Optionally, the bimetallic oxide is selected from zinc aluminum oxide and magnesium aluminum oxide.

[0016] Optionally, the Dv50 of the bimetallic oxide is 200nm to 500nm.

[0017] Optionally, the aspect ratio of the fibrous polyimide is 2.5-10.

[0018] Optionally, the diameter of the fibrous polyimide is 100 nm to 200 nm, and the length of the fibrous polyimide is 500 nm to 1000 nm.

[0019] Optionally, the non-fluorinated polyacrylate includes one or more of styrene-polydimethyl acrylate, styrene-polyethyl acrylate and octyl acrylate.

[0020] Optionally, the primary particle size of the non-fluorinated polyacrylate is 200 nm to 500 nm.

[0021] In the second aspect, the present application also provides a method for preparing a battery separator, comprising the following steps: providing a base film; preparing a first adhesive layer, wherein the first adhesive layer is located on one side of the base film; preparing a heat-resistant layer, wherein the heat-resistant layer is located on the side of the base film away from the first adhesive layer; preparing a second adhesive layer, wherein the second adhesive layer is located on the side of the heat-resistant layer away from the base film; wherein the thicknesses of the base film, the first adhesive layer, the heat-resistant layer and the second adhesive layer satisfy: H2>H1+H3, C2=(0.6~1.2)*(H1+H3) / H2%, and C1=(0.1~0.3)*H2 / H1%.

[0022] In a third aspect, the present application also provides a battery comprising a positive electrode sheet, a negative electrode sheet and a battery separator, wherein the battery separator is the battery separator in any of the above embodiments; or the battery separator is prepared by the preparation method of the above battery separator.

[0023] In a fourth aspect, the present application also provides an electrical device, including the battery in the above embodiment. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The following detailed description of the specific embodiments of the present application in conjunction with the accompanying drawings will make the technical solutions and other beneficial effects of the present application apparent.

[0025] FIG1 is a schematic structural diagram of a battery separator provided in an embodiment of the present application;

[0026] FIG2 is a schematic structural diagram of a battery separator provided in a comparative example of the present application; DETAILED DESCRIPTION

[0027] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the embodiments described are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without making creative efforts are within the scope of protection of this application.

[0028] The disclosure below provides many different embodiments or examples to realize the different structures of the present application. In order to simplify the disclosure of the present application, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present application.

[0029] In the hot composite lamination process, the diaphragm coating used is a mixture of oxide or boehmite and large particle balls, which has poor heat resistance and high membrane rupture performance. For battery cells with high safety requirements, it is difficult to meet the battery cell heat spread and hot box requirements. During use, there is a risk of spherical material falling off, resulting in poor adhesion to the negative electrode sheet. In addition, powder loss will also occur during the friction with the roller, resulting in an increased risk of foreign matter being introduced into the battery cell.

[0030] The first embodiment of the present application provides a battery separator, as shown in Figure 1, including: a base film 10; a first adhesive layer 20, located on one side of the base film 10, the first adhesive layer 20 has a first thickness H1μm, and the first adhesive layer 20 has a first coverage rate C1% on the base film 10; a heat-resistant layer 30, located on the side of the base film 10 away from the first adhesive layer 20, the heat-resistant layer 30 has a second thickness H2μm; a second adhesive layer 40, located on the side of the heat-resistant layer 30 away from the base film 10, the second adhesive layer has a third thickness H3μm, and the second adhesive layer has a second coverage rate C2% on the heat-resistant layer 30; satisfying: H2>H1+H3, C2=(0.6~1.2)*(H1+H3) / H2%, C1=(0.1~0.3)*H2 / H1%.

[0031] By setting an asymmetric diaphragm structure, a first adhesive layer 20 is set on the side of the battery diaphragm in contact with the positive electrode, and a double-layer structure of a heat-resistant layer 30 and a second adhesive layer 40 is set on the side of the battery diaphragm in contact with the negative electrode, and at the same time, the three functional layers are set to meet the relationship of H2>H1+H3, C2=(0.6~1.2)*(H1+H3) / H2%, and C1=(0.1~0.3)*H2 / H1%, so that the battery diaphragm has excellent heat resistance and improves the overall safety of the battery. In addition, in the process of compounding the diaphragm and the electrode, the bonding requirements are met after passing through the hot composite roller, which can effectively avoid the powder loss phenomenon caused by the battery diaphragm and the electrode passing through the roller.

[0032] In some embodiments, the first thickness H1 of the first adhesive layer 20 is 0.5 μm to 1.5 μm. It is understood that the value of H1 (unit: μm) can be any one of 0.5, 0.7, 0.9, 1.1, 1.3, and 1.5, or a range between any two values. The first adhesive layer 20 is used to achieve adhesion between the battery separator and the battery positive electrode. When the first thickness H1 falls within the above value range, it can ensure that the first adhesive layer 20 has ideal adhesion.

[0033] In some embodiments, the second thickness H2 of the heat-resistant layer 30 is between 1.5 μm and 3 μm. It is understood that the value of H2 (unit: μm) can be any one of 1.5, 2.0, 2.5, and 3.0, or a range between any two values. When the second thickness H2 falls within the above range, the heat-resistant layer 30 can have a higher film rupture temperature and lower thermal shrinkage.

[0034] In some embodiments, the third thickness H3 of the second adhesive layer 40 is 0.5 μm to 1 μm. It is understood that the value of H3 (unit: μm) can be any one of 0.5, 0.6, 0.7, 0.8, 0.9, and 1, or a range between any two values. The second adhesive layer 40 is used to achieve adhesion between the battery separator and the battery negative electrode. When the third thickness H3 meets the above value range, it can ensure that the second adhesive layer 40 has ideal adhesion.

[0035] In some embodiments, the coverage of the first adhesive layer 20 is 30-50%.

[0036] In some embodiments, the coverage of the second adhesive layer 40 is 40-60%. It is understood that the value of C1 can be any value among 30%, 35%, 40%, 45%, 50%, or a range between any two values, and the value of C2 can be any value among 40%, 45%, 50%, 55%, or 60%, or a range between any two values. When the coverage of the first adhesive layer 20 or the second adhesive layer 40 falls within the above ranges, a good bonding effect is achieved.

[0037] In some embodiments, the material of the first adhesive layer 20 includes polyvinylidene fluoride (PVDF).

[0038] In some embodiments, the material of the heat-resistant layer 30 includes a bimetallic oxide and a fibrous polyimide (PI). The bimetallic oxide has a layered structure, which facilitates the transport of lithium ions and the adsorption of manganese ions in the battery, preventing the dissolution of manganese ions from the positive electrode during operation, which damages the SEI and causes loss of active lithium. It also has thermal stability and can maintain structural stability even under high temperature conditions. PI has excellent heat resistance, with a heat resistance temperature of up to 400°C. The use of a fibrous polyimide modified with hydrophobic groups can improve the water absorption properties of conventional polyimide on the basis of heat resistance, preventing moisture absorption by the heat-resistant layer 30.

[0039] In some embodiments, the material of the second adhesive layer 40 includes non-fluorinated polyacrylate. Fluorinated polyacrylate is not only cheaper than PVDF, but also has at least double the bonding strength of PVDF. While ensuring the proper bonding between the battery separator and the negative electrode and preventing the negative electrode from falling off during bonding, it can also reduce usage and lower costs.

[0040] In some embodiments, the primary particle size of polyvinylidene fluoride is 100 nm to 300 nm. It is understood that the primary particle size of polyvinylidene fluoride (unit: nm) can be any one of 100, 150, 200, 250, 300 or a range between any two values.

[0041] In some embodiments, the mass ratio of the bimetallic oxide to the fibrous polyimide is 1.3 to 3:1. It is understandable that the mass ratio of the bimetallic oxide to the fibrous polyimide can be any one of 1.3, 1.5, 2, 2.5, 3 or a range between any two values.

[0042] In some embodiments, the bimetallic oxide is selected from zinc aluminum oxide or magnesium aluminum oxide.

[0043] In some embodiments, the Dv50 of the bimetallic oxide is between 200 nm and 500 nm, where Dv50 is the particle size at which the cumulative volume percentage of the bimetallic oxide particles reaches 50%. It is understood that the Dv50 (unit: nm) of the bimetallic oxide can be any one of 200, 250, 300, 350, 400, 450, and 500, or a range between any two values. As one of the primary materials of the heat-resistant layer 30, the particle size of the bimetallic oxide affects the heat resistance of the coating. Larger particle sizes affect the bulk density of the coating, which in turn affects the heat resistance. When the particle size of the bimetallic oxide falls within the aforementioned range, thermal shrinkage can be effectively reduced.

[0044] In some embodiments, the aspect ratio of the fibrous polyimide is 2.5 to 10. It is understood that the aspect ratio of the fibrous polyimide can be any one of 2.5, 4, 5.5, 7, 8.5, 10 or a range between any two values.

[0045] In some embodiments, the diameter of the fibrous polyimide is 100 nm to 200 nm, and the length of the fibrous polyimide is 500 nm to 1000 nm. It is understood that the diameter of the fibrous polyimide (unit: nm) can be any one of 100, 120, 140, 160, 180, 200, or a range between any two values, and the length of the fibrous polyimide (unit: nm) can be any one of 500, 600, 700, 800, 900, or 1000, or a range between any two values. When the aspect ratio of the fibrous polyimide in the heat-resistant layer 30 meets the above value range, a network structure can be constructed. At the same time, the bimetallic oxide plays a filling role in the network structure. The two cooperate with each other, allowing the battery separator to not only maintain its intact shape under high temperature conditions, but also significantly increase the membrane rupture temperature, thereby improving battery safety.

[0046] In some embodiments, the non-fluorinated polyacrylate includes one or more of styrene-polydimethyl acrylate, styrene-polyethyl acrylate, or hexyl octyl acrylate.

[0047] In some embodiments, the primary particle size of the non-fluorinated polyacrylate is 200 nm to 500 nm. It can be understood that the primary particle size of the non-fluorinated polyacrylate (unit: nm) can be any one of 200, 300, 400, 500 or a range between any two values.

[0048] The second embodiment of the present application provides a method for preparing a battery separator, comprising the following steps: providing a base film 10; preparing a first adhesive layer 20, wherein the first adhesive layer 20 is located on one side of the base film 10; preparing a heat-resistant layer 30, wherein the heat-resistant layer 30 is located on the side of the base film 10 away from the first adhesive layer 20; preparing a second adhesive layer 40, wherein the second adhesive layer 40 is located on the side of the heat-resistant layer 30 away from the base film 10; wherein the thicknesses of the base film 10, the first adhesive layer 20, the heat-resistant layer 30 and the second adhesive layer 40 satisfy: H2>H1+H3, C2=(0.6~1.2)*(H1+H3) / H2%, and C1=(0.1~0.3)*H2 / H1%.

[0049] Specifically, the preparation method of the battery separator can be achieved through the following steps: S1, selecting a base film 10; S2, preparing a first adhesive layer 20: configuring PVDF, carboxymethyl cellulose (CMC), adhesive and dispersant into an aqueous solution in a certain proportion, coating it on one side of the base film 10, and baking to obtain the first adhesive layer 20; S3, preparing a heat-resistant layer 30: configuring bimetallic oxide, fibrous PI, dispersant, CMC, adhesive and wetting agent into an aqueous solution in a certain proportion, coating it on the other side of the base film 10, and baking to obtain the heat-resistant layer 30; S4, preparing a second adhesive layer 40: configuring non-fluorinated polyacrylate, CMC, adhesive and dispersant into an aqueous solution in a certain proportion, coating it on the surface of the heat-resistant layer 30, and baking to obtain the second adhesive layer 40, thereby completing the preparation of the battery separator.

[0050] Wherein, the adhesive used in the above preparation method can be polyacrylonitrile-polymethacrylic acid or styrene-butadiene rubber (SBR); the dispersant can be sodium polyacrylate.

[0051] A third embodiment of the present application provides a battery, comprising a positive electrode sheet and a negative electrode sheet, wherein a battery separator according to any of the above embodiments is provided between the positive electrode sheet and the negative electrode sheet.

[0052] A fourth embodiment of the present application provides an electrical device, comprising the battery in the above embodiment.

[0053] The battery provided in this application is described below with reference to specific embodiments:

[0054] Example 1

[0055] This embodiment provides a battery separator, a battery, and methods for preparing the same.

[0056] As shown in Figure 1, the battery separator includes a base film 10, a first adhesive layer 20, a heat-resistant layer 30, and a second adhesive layer 40. The first adhesive layer 20 is located on one side of the base film 10, the heat-resistant layer 30 is located on the other side of the base film 10, and the second adhesive layer 40 is located on the side of the heat-resistant layer 30 away from the base film 10.

[0057] The battery separator in this embodiment is prepared by the following method:

[0058] S1. A wet-process diaphragm is selected as the base membrane 10, with a thickness of 9 μm and a porosity of 40%.

[0059] S2. Preparation of the first adhesive layer 20: Dongyang Sunshine PVDF with an average particle size of 190 nm was selected. The raw materials were mixed in a weight ratio of 84% PVDF: CMC: polyacrylonitrile-polymethacrylic acid: SBR: sodium polyacrylate (84%): 0.8%: 7.6%: 0.9%: 6.7%. Water was used as the solvent, and a slurry was prepared to a solids content of 6%. The prepared slurry was applied to one side of the base film 10 using a gravure roller and baked at 65°C for 5 minutes to obtain the first adhesive layer 20 with a thickness of 0.8 μm and a coverage of 40%.

[0060] S3. Preparation of Heat-Resistant Layer 30: Zinc-aluminum oxide with a Dv50 of 300 nm and modified fibrous polyimide (PI) with a diameter of 150 nm and a length of 700 nm were selected. The raw materials were mixed in a weight ratio of 54.69% zinc-aluminum oxide to fibrous polyimide (PI): dispersant: CMC: binder: wetting agent = 54.69%: 36.46%: 0.42%: 1.12%: 7.18%: 0.13%. A slurry was prepared using water as the solvent, with a solids content of 35%. The prepared slurry was applied to the other side of the base film 10 using a gravure roller and baked at 75°C for 5 minutes to produce a heat-resistant layer 30 with a thickness of 2 μm.

[0061] S4. Preparation of the second adhesive layer 40: Styrene-polymethyl acrylate with a primary particle size of 300 nm was selected and mixed in a weight ratio of 84% styrene-polymethyl acrylate: CMC: adhesive: dispersant = 6.7%. Water was used as the solvent, and a slurry was prepared with a solid content of 6%. The prepared slurry was applied to the surface of the heat-resistant layer 30 using a gravure roller and baked at 75°C for 5 minutes to obtain the second adhesive layer 40 with a thickness of 0.7 μm and a coverage of 50%. This completed the preparation of the battery separator.

[0062] The steps for preparing a battery using the above-mentioned battery separator are as follows:

[0063] 1) Preparation of positive electrode sheet: lithium iron phosphate is used as the main material, and the rest are PVDF, conductive agent, etc. to prepare slurry. The positive electrode accounts for 95.6% of the coating. The prepared slurry is applied to carbon-coated aluminum foil to obtain the positive electrode sheet.

[0064] 2) Preparation of negative electrode sheets: artificial graphite, CMC, conductive agent and SBR are used to prepare slurry, which is coated on copper foil and processed to produce negative electrode sheets. The negative electrode accounts for 95.5% of the coating.

[0065] 3) Making a diaphragm-negative electrode monolith: The battery diaphragm and the negative electrode sheet are bonded together using a hot roller hot pressing process with a temperature of 90°C. The unit formed after hot pressing is cut into single sheets with a hot cutter to form a diaphragm-negative electrode-diaphragm monolithic structure.

[0066] 4) Preparation of electrode group: The separator-negative electrode sheet and the positive electrode sheet are stacked into an electrode group in the form of a laminate, and hot pressed at 90° C. using a hot press to complete the production of the electrode group.

[0067] 5) Packaging and injection: The prepared electrode group is packaged in a soft package and then injected with electrolyte.

[0068] 6) Pre-charging and formation: Pre-charging and forming the battery cell to obtain the battery of the present invention.

[0069] Examples 2 to 13

[0070] The battery separators and battery structures provided in Examples 2 to 13 are the same, with only structural parameters and material parameters being adjusted.

[0071] The relevant structural parameters of the battery separators of Examples 1 to 13 are shown in Table 1, and the material parameters are shown in Table 2.

[0072] Table 1

[0073] Table 2

[0074] Comparative Example 1

[0075] A commercial battery separator produced by Shanghai Enjie Company was selected, as shown in FIG2 . The battery separator in this comparative example includes:

[0076] The base film 10 is a wet-process membrane with a thickness of 9 μm and a porosity of 40%.

[0077] The first adhesive layer 20 has a thickness of 1 μm and is made of PVDF powder;

[0078] The heat-resistant layer 30 has a thickness of 2 μm and is made of a mixture of boehmite and spherical polyacrylate materials with a primary particle size of 4-7 μm.

[0079] A battery was prepared by a conventional method using the above-mentioned battery separator.

[0080] The batteries prepared in the above examples and comparative examples were subjected to formation, capacity separation, strength performance and safety performance tests.

[0081] Strength performance test method is as follows:

[0082] (1) Adhesion test:

[0083] The adhesion test was performed with the diaphragm folded in half, under the following conditions: temperature 90°C, surface pressure 1 MPa, and time 60 seconds.

[0084] (2) Thermal shrinkage test: refer to GB / T36363-2018, test temperature 130℃ / h and 150℃ / h.

[0085] (3) Membrane rupture temperature test: Use the TMA test method and raise the temperature from room temperature (25°C).

[0086] The safety performance test method is as follows:

[0087] (1) Heat spread test:

[0088] 1C constant current constant voltage charging to 3.65V, cut-off current 0.05C, 100% SOC;

[0089] Fix the two battery cells with a clamp, fix a heating plate on the positive electrode of the first battery cell, heat the battery cell until thermal runaway occurs, stop heating, and record the heat spread time.

[0090] (2) Hot box test:

[0091] Charge at 0.5C constant current and constant voltage to 4.2V, then cut down to 4.2V constant voltage at 0.05C. Record the charging process data (V / T / I), and measure and record the battery cell voltage and internal resistance.

[0092] The exterior is fixed with glass clamps;

[0093] The temperature box is raised from the test environment temperature to 130℃±2℃ at a rate of 5℃ / min and maintained at this temperature for 30 minutes, then raised to 135℃±2℃ and maintained at this temperature for 30 minutes, then raised to 140±2℃ and maintained at this temperature for 30 minutes, and so on, until the battery thermal runaway occurs.

[0094] The test results after testing are shown in Table 3.

[0095] Table 3

[0096] According to the test results in Table 3, it can be seen that the battery separator structure provided by the present application has good adhesion and heat resistance. When the thickness and coverage of the first adhesive layer 20, the heat-resistant layer 30 and the second adhesive layer 40 simultaneously satisfy H2>H1+H3, C2=(0.6~1.2)*(H1+H3) / H2%, and C1=(0.1~0.3)*H2 / H1%, the adhesion of the battery separator, especially the adhesion on the negative electrode side, can be greatly improved. At the same time, the prepared battery also has significant improvements in various heat resistance properties such as thermal shrinkage performance and membrane rupture temperature, which can meet the needs of products with higher safety requirements.

[0097] The above is a detailed introduction to a battery separator and preparation method, battery, and electrical equipment provided in the embodiments of the present application. Specific examples are used in this application to illustrate the principles and implementation methods of the present application. The description of the above embodiments is only used to help understand the technical solutions and core ideas of the present application; ordinary technicians in this field should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present application.

[0098] Reference numerals: 10 - base film, 20 - first adhesive layer, 30 - heat-resistant layer, 40 - second adhesive layer.

Claims

1. A battery separator, comprising: Basement membrane; A first adhesive layer, located on one side of the base film, the first adhesive layer having a first thickness H1 μm, and the first adhesive layer having a first coverage C1% on the base film; a heat-resistant layer, located on a side of the base film away from the first adhesive layer, the heat-resistant layer having a second thickness H2 μm; a second adhesive layer, located on a side of the heat-resistant layer away from the base film, the second adhesive layer having a third thickness H3 μm, and the second adhesive layer having a second coverage C2% for the heat-resistant layer; It satisfies: H2>H1+H3, C2=(0.6~1.2)*(H1+H3) / H2%, and C1=(0.1~0.3)*H2 / H1%.

2. A battery separator according to claim 1, wherein: The battery separator meets at least one of the following characteristics: The first thickness H1 of the first adhesive layer is 0.5 μm to 1.5 μm; The second thickness H2 of the heat-resistant layer is 1.5 μm to 3 μm; The third thickness H3 of the second adhesive layer is 0.5 μm to 1 μm.

3. A battery separator according to any one of claims 1 to 2, wherein: The battery separator meets at least one of the following characteristics: The first coverage C1 is 30-50%; The second coverage C2 is 40-60%.

4. A battery separator according to any one of claims 1 to 3, wherein: The battery separator meets at least one of the following characteristics: The material of the first bonding layer includes polyvinylidene fluoride; The material of the heat-resistant layer includes bimetallic oxide and fibrous polyimide; The material of the second adhesive layer includes non-fluorine-based polyacrylate.

5. A battery separator according to claim 4, wherein: The primary particle size of the polyvinylidene fluoride is 100nm to 300nm.

6. A battery separator according to any one of claims 4 to 5, wherein: The battery separator meets at least one of the following characteristics: The mass ratio of the bimetallic oxide to the fibrous polyimide is (1.3-3):1; The bimetallic oxide is selected from zinc aluminum oxide or magnesium aluminum oxide; The Dv50 of the bimetallic oxide is 200nm to 500nm; The aspect ratio of the fibrous polyimide is 2.5 to 10; The diameter of the fibrous polyimide is 100 nm to 200 nm, and the length of the fibrous polyimide is 500 nm to 1000 nm.

7. A battery separator according to any one of claims 4 to 6, wherein: The battery separator meets at least one of the following characteristics: The non-fluorinated polyacrylate includes one or more of styrene-polydimethyl acrylate, styrene-polyethyl acrylate or octyl acrylate; The primary particle size of the non-fluorine-based polyacrylate is 200nm to 500nm.

8. A method for preparing a battery separator, wherein: The steps include: providing a basement membrane; preparing a first adhesive layer, wherein the first adhesive layer is located on one side of the base film; preparing a heat-resistant layer, wherein the heat-resistant layer is located on a side of the base film away from the first adhesive layer; preparing a second adhesive layer, wherein the second adhesive layer is located on a side of the heat-resistant layer away from the base film; Wherein, the thickness of the base film, the first adhesive layer, the heat-resistant layer and the second adhesive layer satisfies: H2>H1+H3, C2=(0.6~1.2)*(H1+H3) / H2%, and C1=(0.1~0.3)*H2 / H1%.

9. A battery comprising a positive electrode sheet, a negative electrode sheet and a battery separator, The battery separator is the battery separator according to any one of claims 1 to 7; or the battery separator is prepared by the preparation method of the battery separator according to claim 8.

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