A battery separator, its preparation method, and a lithium-ion battery

Abstract

This invention discloses a battery separator, its preparation method, and a lithium-ion battery. The battery separator includes a base film and a functional coating. The functional coating is applied to at least one surface of the base film and contains ceramic materials and 1,3-propanediol cyclic carbonate. The preparation method of the battery separator includes: (1) mechanically pulverizing 1,3-propanediol cyclic carbonate and preparing a saturated solution with water; (2) preparing a binder and the saturated solution obtained in step (1) into a glue solution; (3) preparing the glue solution obtained in step (2) with ceramic materials and 1,3-propanediol cyclic carbonate into a functional coating slurry; (4) uniformly coating the functional coating slurry obtained in step (3) onto at least one surface of the base film to obtain the battery separator. This invention optimizes the coating structure and process to achieve the safety performance of the separator while ensuring that the porosity does not decrease significantly, thereby improving the high-rate performance of the battery.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery technology, and in particular to a battery separator, its preparation method, and a lithium-ion battery. Background Technology

[0002] Currently, high-rate batteries are mainly improved by nanomaterials, increasing electrolyte conductivity, and improving separator porosity. The separator is located between the positive and negative electrodes. Lithium ions are extracted from the positive electrode, solubilized in the electrolyte, and then enter the negative electrode through the separator to desolvate and embed into the negative electrode. The separator has a large obstruction effect in the whole process. Improving the separator porosity and pore size distribution can significantly improve the rate performance.

[0003] High-rate batteries require high porosity in the separator. High porosity results in fast lithium-ion diffusion, but the base film with high porosity has poor thermal stability and is prone to shrinkage at high temperatures. While coating the separator improves thermal stability, it reduces porosity, leading to a decrease in lithium-ion migration speed, making it unsuitable for high-rate discharge.

[0004] Therefore, in order to improve safety while ensuring that porosity does not decrease significantly, it is indeed necessary to provide a technical solution to address the above problems. Summary of the Invention

[0005] One of the objectives of this invention is to provide a battery separator that optimizes the separator coating process, achieves the safety performance of the separator, and ensures that the porosity does not decrease significantly, thereby improving the high-rate performance of the battery.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A battery separator, characterized in that it comprises:

[0008] Base film;

[0009] A functional coating is applied to at least one surface of the base film, the functional coating containing a ceramic material and 1,3-propanediol cyclic carbonate.

[0010] Preferably, the functional coating further comprises an adhesive, the adhesive comprising at least one of polytetrafluoroethylene, polyacrylate and waterborne polyurethane.

[0011] Preferably, the ceramic material includes at least one of alumina, boehmite, zirconium oxide, magnesium oxide, silicon oxide, and calcium oxide.

[0012] Preferably, the base film is at least one of polyethylene, polypropylene, polyimide, and nonwoven fabric.

[0013] Preferably, the particle size D50 of the 1,3-propanediol cyclic carbonate is 10-1000 nm.

[0014] Preferably, the thickness of the functional coating is 1-5 μm.

[0015] Preferably, the 1,3-propanediol cyclic carbonate in the functional coating can dissolve and vaporize at a preset temperature to form a porous structure, wherein the preset temperature is >47°C.

[0016] A second objective of this invention is to provide a method for preparing a battery separator, comprising the following steps:

[0017] (1) The 1,3-propanediol cyclic carbonate was mechanically pulverized and mixed with water to form a saturated solution;

[0018] (2) Prepare an adhesive solution by mixing the adhesive with the saturated solution obtained in step (1);

[0019] (3) The adhesive obtained in step (2) is combined with ceramic material and 1,3-propanediol cyclic carbonate to form a functional coating slurry;

[0020] (4) The functional coating slurry obtained in step (3) is uniformly coated on at least one surface of the base film to obtain the battery separator.

[0021] Preferably, in step (1), the pulverizing temperature is <30°C.

[0022] Preferably, in step (2), the mass ratio of the adhesive to the saturated solution is (93-97):(3-7), and more preferably 95:5.

[0023] Preferably, in step (3), the mass ratio of the adhesive, the ceramic material and the 1,3-propanediol cyclic carbonate is (58-62):(18-22):(18-22), and more preferably 60:20:20.

[0024] Preferably, in step (4), the coating temperature is >80°C.

[0025] A third objective of this invention is to provide a lithium-ion battery, comprising a positive electrode, a negative electrode, and a separator spaced between the positive electrode and the negative electrode, wherein the separator is any of the separators described above.

[0026] The beneficial effects of this invention are as follows: The separator provided by this invention has a functional coating containing ceramic materials and 1,3-propanediol cyclic carbonate coated on at least one surface of the base film. At a certain temperature, the 1,3-propanediol cyclic carbonate vaporizes to form a porous structure, thereby preventing a significant decrease in the thermal stability and porosity of the separator. This invention achieves the safety performance of the separator by optimizing the coating structure and process, while ensuring that the porosity does not decrease significantly, thus improving the high-rate performance of the battery. It solves the problem that existing separators, after coating, improve thermal stability, but reduce the separator porosity, resulting in a decrease in lithium-ion migration speed and unsuitability for high-rate discharge. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of a battery separator structure according to an embodiment of this application.

[0028] Figure 2 This is a schematic diagram of a battery separator structure according to another embodiment of this application.

[0029] In the figure, 1 is the base film; 2 is the functional coating; 21 is 1,3-propanediol cyclic carbonate; and 22 is the ceramic material. Detailed Implementation

[0030] A first aspect of the present invention is to provide a battery separator comprising a base film and a functional coating coated on at least one surface of the base film, the functional coating comprising a ceramic material and 1,3-propanediol cyclic carbonate.

[0031] In one embodiment of the invention, the functional coating further comprises an adhesive, the adhesive comprising at least one of polytetrafluoroethylene, polyacrylate and waterborne polyurethane.

[0032] In one embodiment of the present invention, the ceramic material includes at least one selected from alumina, boehmite, zirconium oxide, magnesium oxide, silicon oxide, and calcium oxide.

[0033] In one embodiment of the present invention, the base film is at least one of polyethylene, polypropylene, polyimide and nonwoven fabric.

[0034] In one embodiment of the present invention, the particle size D50 of the 1,3-propanediol cyclic carbonate is 10-1000 nm. Grinding the particle size D50 within this range is beneficial for both the formation of a porous structure and for better coating.

[0035] In one embodiment of the invention, the thickness of the functional coating is 1-5 μm. If the thickness of the functional coating is too small, the improvement in the coefficient of thermal shrinkage is minimal; if the thickness of the functional coating is too large, the battery energy density decreases.

[0036] In one embodiment of the present invention, the 1,3-propanediol cyclic carbonate in the functional coating can dissolve and vaporize at a preset temperature to form a porous structure, wherein the preset temperature is >47°C. For example, it can be 50°C, 60°C, 70°C, 80°C, 90°C, 100°C, 110°C, or 120°C, preferably 80~120°C. Since the melting point of 1,3-propanediol cyclic carbonate is approximately 47°C, the dissolution and vaporization of 1,3-propanediol cyclic carbonate to form a porous structure can only be achieved within this predetermined temperature range.

[0037] A second aspect of the present invention is to provide a method for preparing a battery separator, comprising the following steps:

[0038] (1) Mechanically pulverize 1,3-propanediol cyclic carbonate and prepare a saturated solution with water;

[0039] (2) Prepare an adhesive solution by mixing the adhesive with the saturated solution obtained in step (1);

[0040] (3) The adhesive obtained in step (2) is combined with ceramic material and 1,3-propanediol cyclic carbonate to form a functional coating slurry;

[0041] (4) The functional coating slurry obtained in step (3) is uniformly coated on at least one surface of the base film to obtain the battery separator.

[0042] Preferably, the pulverization temperature is <30°C. This pulverization temperature helps prevent the 1,3-propanediol cyclic carbonate from melting.

[0043] In one embodiment of the present invention, the mass ratio of the binder to the saturated solution is (93-97):(3-7). Preferably, it is 95:5, mainly to ensure that the viscosity of the slurry is moderate. If the mass ratio is too large, the viscosity will be too high; if it is too small, the viscosity will be too low, both of which are not conducive to the subsequent steps.

[0044] In one embodiment of the present invention, the mass ratio of the adhesive, the ceramic material, and the 1,3-propanediol cyclic carbonate is (58-62):(18-22):(18-22), preferably 60:20:20. The ceramic material Al2O3 serves as both an insulating and heat-insulating layer, while also enhancing the thermal shrinkage capacity of the diaphragm. The 1,3-propanediol cyclic carbonate primarily aims to create pores on the coating surface, and the adhesive acts as an adhesive. Excessive binder in the adhesive results in excessive viscosity; excessive Al2O3 reduces porosity; and excessive 1,3-propanediol cyclic carbonate leads to excessive pores and a high coefficient of thermal shrinkage. Therefore, controlling the mass ratio of the three components within the aforementioned range better balances the relationship between viscosity, porosity, and coefficient of thermal shrinkage.

[0045] In one embodiment of the invention, the coating temperature is >80°C. For example, it can be 85°C, 90°C, 100°C, 110°C, 120°C, 130°C, or 140°C, preferably 90~120°C. The oven of the coating machine is under negative pressure, causing the saturated vapor pressure to decrease and its evaporation temperature to drop. After the solid melts, it can evaporate at a lower temperature. Therefore, within this coating temperature range, 1,3-propanediol cyclic carbonic acid can better dissolve and vaporize to form a porous structure.

[0046] A third aspect of the present invention is to provide a lithium-ion battery, comprising a separator, a positive electrode, a negative electrode, and an electrolyte provided by the present invention.

[0047] The positive electrode includes a positive current collector and a positive active material layer coated on at least one surface of the positive current collector. The positive active material layer may be, but is not limited to, a chemical formula such as Li. a Ni x Co y M z O 2 b N b (where 0.95≤a≤1.2, x>0, y≥0, z≥0, and x+y+z=1, 0≤b≤1, M is selected from one or more combinations of Mn and Al, and N is selected from one or more combinations of F, P, and S) The positive electrode active material may also be, but is not limited to, LiCoO2, LiNiO2, LiVO2, LiCrO2, LiMn2O4, LiCoMnO4, Li2NiMn3O8, LiNi 0.5 Mn 1.5 The positive electrode active material can be one or more combinations of O4, LiCoPO4, LiMnPO4, LiFePO4, LiNiPO4, LiCoFSO4, CuS2, FeS2, MoS2, NiS, and TiS2. The positive electrode active material can also be modified. Methods for modifying the positive electrode active material are known to those skilled in the art. For example, coating, doping, and other methods can be used to modify the positive electrode active material. The materials used for modification can be one or more combinations of Al, B, P, Zr, Si, Ti, Ge, Sn, Mg, Ce, and W, including but not limited to. The positive electrode current collector can be aluminum foil.

[0048] The negative electrode sheet includes a negative electrode current collector and a negative electrode active material layer coated on at least one surface of the negative electrode current collector. The negative electrode active material layer can be one or more of the following: graphite, soft carbon, hard carbon, carbon fiber, mesophase carbon microspheres, silicon-based materials, tin-based materials, lithium titanate, or other metals that can form alloys with lithium. Specifically, the graphite can be selected from one or more of artificial graphite, natural graphite, and modified graphite; the silicon-based material can be selected from one or more of elemental silicon, silicon oxide compounds, silicon-carbon composites, and silicon alloys; and the tin-based material can be selected from one or more of elemental tin, tin oxide compounds, and tin alloys. The negative electrode current collector can be copper foil, PET copper foil, or aluminum foil.

[0049] The electrolyte can be any conventional electrolyte, such as a non-aqueous electrolyte. The non-aqueous electrolyte is a solution of an electrolyte lithium salt in a non-aqueous solvent, and can be any conventional non-aqueous electrolyte known to those skilled in the art. For example, the electrolyte can be selected from at least one of lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium tetrafluoroborate (LiBF4), lithium hexafluoroarsenate (LiAsF6), and lithium hexafluorosilicate (LiSiF6). The non-aqueous solvent can be selected from a mixed solution of linear and cyclic esters, wherein the linear ester can be at least one of dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), methyl propyl carbonate (MPC), and dipropyl carbonate (DPC). The cyclic ester can be at least one of ethylene carbonate (EC), propylene carbonate (PC), and vinylene carbonate (VC).

[0050] To make the technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0051] Example 1

[0052] like Figure 1 As shown, this embodiment provides a diaphragm, including a base membrane 1 and a functional coating 2. The functional coating 2 is uniformly coated on one surface of the base membrane 1. The base membrane 1 is a polyethylene membrane. The functional coating 2 includes 1,3-propanediol cyclocarbonate 21, ceramic material 22 and polytetrafluoroethylene binder. The 1,3-propanediol cyclocarbonate 21 in the functional coating 2 can dissolve and vaporize at a predetermined temperature (>47°C) and form a porous structure on the surface of the functional coating 2.

[0053] The method for preparing the battery separator includes the following steps:

[0054] (1) 1,3-propanediol cyclic carbonate was mechanically pulverized at a temperature of 25°C to obtain a particle size D50 of 25 nm. 1,3-propanediol cyclic carbonate was then mixed with water to form a saturated solution.

[0055] (2) Prepare an adhesive solution by mixing the adhesive with the saturated solution obtained in step (1) at a mass ratio of 95:5;

[0056] (3) The adhesive obtained in step (2) is mixed with ceramic material and 1,3-propanediol cyclic carbonate in a mass ratio of 60:20:20 to form a functional coating slurry;

[0057] (4) The functional coating slurry obtained in step (3) is uniformly coated on a surface of the base film at a coating temperature of 95°C and a coating thickness of 2μm to obtain the battery separator.

[0058] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 43%, a thermal shrinkage rate of 1.7% at 130°C, an internal resistance of 1.6mΩ, and a voltage drop of 220mV at 10C / 10s when charged to 50% (SOC).

[0059] Example 2

[0060] The difference between this embodiment and Embodiment 1 is the preparation of the battery separator:

[0061] (1) 1,3-propanediol cyclic carbonate was mechanically pulverized at a temperature of 25°C to obtain a particle size D50 of 35 nm. 1,3-propanediol cyclic carbonate was then mixed with water to form a saturated solution.

[0062] (2) Prepare an adhesive solution by mixing the adhesive with the saturated solution obtained in step (1) at a mass ratio of 95:5;

[0063] (3) The adhesive obtained in step (2) is mixed with ceramic material and 1,3-propanediol cyclic carbonate in a mass ratio of 60:20:20 to form a functional coating slurry;

[0064] (4) The functional coating slurry obtained in step (3) is uniformly coated on a surface of the base film at a coating temperature of 100°C and a coating thickness of 4μm to obtain the battery separator.

[0065] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 40%, a thermal shrinkage rate of 1.2% at 130°C, an internal resistance of 1.8mΩ, and a voltage drop of 250mV at 10C / 10s when charged to 50% (SOC).

[0066] Example 3

[0067] like Figure 2 As shown, the difference between this embodiment and embodiment 1 is that in step (4), the functional coating slurry is uniformly coated on both surfaces of the base film, with a coating thickness of 2 μm on each surface.

[0068] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 40%, a thermal shrinkage rate of 1.2% at 130°C, an internal resistance of 1.8mΩ, and a voltage drop of 250mV at 10C / 10s when charged to 50% (SOC).

[0069] Example 4

[0070] The difference between this embodiment and embodiment 1 is that in step (4), the functional coating slurry is uniformly coated on one surface of the base film with a coating thickness of 1 μm.

[0071] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 40%, a thermal shrinkage rate of 1.8% at 130°C, an internal resistance of 1.65mΩ, and a voltage drop of 240mV at 10C / 10s when charged to 50% (SOC).

[0072] Example 5

[0073] The difference between this embodiment and embodiment 1 is that in step (4), the functional coating slurry is uniformly coated on one surface of the base film with a coating thickness of 3 μm.

[0074] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 42%, a thermal shrinkage rate of 1.8% at 130°C, an internal resistance of 1.7mΩ, and a voltage drop of 245mV at 10C / 10s when charged to 50% (SOC).

[0075] Example 6

[0076] The difference between this embodiment and embodiment 1 is that in step (4), the functional coating slurry is uniformly coated on both surfaces of the base film, with a coating thickness of 1 μm on each surface.

[0077] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 42%, a thermal shrinkage rate of 1.5% at 130°C, an internal resistance of 1.7mΩ, and a voltage drop of 230mV at 10C / 10s when charged to 50% (SOC).

[0078] Example 7

[0079] The difference between this embodiment and embodiment 1 is that in step (4), the functional coating slurry is uniformly coated on both surfaces of the base film, with a coating thickness of 4 μm on each surface.

[0080] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 40%, a thermal shrinkage rate of 1.3% at 130°C, an internal resistance of 1.85mΩ, and a voltage drop of 250mV at 10C / 10s when charged to 50% (SOC).

[0081] Example 8

[0082] The difference between this embodiment and embodiment 1 is that in step (4), the functional coating slurry is uniformly coated on both surfaces of the base film, with a coating thickness of 3 μm on each surface.

[0083] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 41%, a thermal shrinkage rate of 1.4% at 130°C, an internal resistance of 1.68mΩ, and a voltage drop of 245mV at 10C / 10s when charged to 50% (SOC).

[0084] Example 9

[0085] The difference between this embodiment and embodiment 1 is that in step (4), the functional coating slurry is uniformly coated on one surface of the base film with a coating thickness of 5 μm.

[0086] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 40%, a thermal shrinkage rate of 1.85% at 130℃, an internal resistance of 1.8mΩ, and a voltage drop of 230mV at 10C / 10s when charged to 50% (SOC).

[0087] Example 10

[0088] The difference between this embodiment and embodiment 1 is that in step (4), the functional coating slurry is uniformly coated on both surfaces of the base film, with a coating thickness of 5 μm on each surface.

[0089] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 40%, a thermal shrinkage rate of 1.35% at 130°C, an internal resistance of 1.66mΩ, and a voltage drop of 250mV at 10C / 10s when charged to 50% (SOC).

[0090] Comparative Example 1

[0091] The difference between this comparative example and Example 1 is that this comparative example uses ceramic material as a functional coating, which is uniformly coated on a surface of a base film to obtain a diaphragm with a coating thickness of 2 μm.

[0092] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 35%, a thermal shrinkage rate of 1.5% at 130°C, an internal resistance of 2.2mΩ, and a voltage drop of 300mV at 10C / 10s when charged to 50% (SOC).

[0093] Comparative Example 2

[0094] The difference between this comparative example and Comparative Example 1 is that the coating thickness of the functional coating is 4 μm.

[0095] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 30%, a thermal shrinkage rate of 1.0% at 130℃, an internal resistance of 2.5mΩ, and a voltage drop of 400mV at 10C / 10s when charged to 50% (SOC).

[0096] Comparative Example 3

[0097] The difference between this comparative example and Comparative Example 1 is that the functional coating is uniformly coated on both surfaces of the base film to obtain a diaphragm, with a coating thickness of 2 μm on each surface.

[0098] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 30%, a thermal shrinkage rate of 1.0% at 130℃, an internal resistance of 2.5mΩ, and a voltage drop of 400mV at 10C / 10s when charged to 50% (SOC).

[0099] Comparative Example 4

[0100] The difference between this comparative example and Comparative Example 1 is that this comparative example uses the base film directly as the battery separator without coating.

[0101] A lithium-ion battery was fabricated using this separator along with positive and negative electrodes. The battery was tested at 5Ah and 10C. The separator had a porosity of 45%, a thermal shrinkage rate of 3.0% at 130℃, an internal resistance of 1.5mΩ, and a voltage drop of 200mV at 10C / 10s when charged to 50% (SOC).

[0102] The battery performance test results of Examples 1-10 and Comparative Examples 1-4 are shown in the table below:

[0103]

[0104] The test results in the table show that the separator prepared by this invention exhibits improved thermal shrinkage at 130℃ without significantly reducing its porosity. The internal resistance of batteries made using this separator and the 10C / 10s voltage drop at 50% charge are lower than those of separators coated with pure ceramic materials, approaching the internal resistance of batteries made directly using the base membrane as the separator. This demonstrates that the functional coating of the separator, containing 1,3-propanediol cyclic carbonate, and the ceramic material possess high porosity and heat resistance, resulting in batteries with good rate performance.

[0105] The test results from Examples 1 and 3 show that, at the same coating thickness, coating both surfaces of the base film improves heat resistance compared to coating only one surface, but reduces membrane porosity, battery internal resistance, and voltage drop. Furthermore, the results from Comparative Examples 1 and 2 indicate that doubling the coating thickness has little effect on porosity, battery internal resistance, and voltage drop, while improving heat resistance. Therefore, a coating thickness of 2 μm is optimal compared to other thicknesses.

[0106] In summary, the separator prepared by coating a base membrane with a slurry made from 1,3-propanediol cyclic carbonate, as described in this invention, exhibits excellent porosity and heat resistance. Batteries made using this separator also show lower internal resistance and voltage drop during high-rate discharge. This invention optimizes the coating structure and process to achieve safe separator performance while ensuring that porosity is not significantly reduced, thus improving the battery's high-rate performance. It solves the problem that while existing separator coatings improve thermal stability, they also reduce membrane porosity, leading to a decrease in lithium-ion migration speed and making them unsuitable for high-rate discharge.

[0107] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A battery separator, characterized in that, include: Base film; A functional coating is applied to at least one surface of the base film, the functional coating containing a ceramic material and 1,3-propanediol cyclic carbonate; The 1,3-propanediol cyclic carbonate in the functional coating can dissolve and vaporize at a preset temperature to form a porous structure, wherein the preset temperature is >47°C; the coating temperature is >80°C; and the coating process is carried out under negative pressure.

2. The battery separator according to claim 1, characterized in that, The functional coating also contains an adhesive, which includes at least one of polytetrafluoroethylene, polyacrylate, and waterborne polyurethane.

3. The battery separator according to claim 1, characterized in that, The ceramic material includes at least one of alumina, boehmite, zirconium oxide, magnesium oxide, silicon oxide, and calcium oxide; the base film is at least one of polyethylene, polypropylene, polyimide, and nonwoven fabric.

4. A battery separator according to claim 1, characterized in that, The particle size D50 of the 1,3-propanediol cyclic carbonate is 10-1000 nm.

5. A battery separator according to claim 1, characterized in that, The thickness of the functional coating is 1-5 μm.

6. A method for preparing a battery separator according to any one of claims 1-5, characterized in that, Includes the following steps: (1) The 1,3-propanediol cyclic carbonate was mechanically pulverized and mixed with water to form a saturated solution; (2) Prepare an adhesive solution by mixing the adhesive with the saturated solution obtained in step (1); (3) The adhesive obtained in step (2) is combined with ceramic material and 1,3-propanediol cyclic carbonate to form a functional coating slurry; (4) The functional coating slurry obtained in step (3) is uniformly coated on at least one surface of the base film to obtain the battery separator.

7. The method for preparing a battery separator according to claim 6, characterized in that, In step (1), the pulverization temperature is <30℃.

8. The method for preparing a battery separator according to claim 6, characterized in that, In step (2), the mass ratio of the adhesive to the saturated solution is (93-97):(3-7).

9. The method for preparing a battery separator according to claim 6, characterized in that, In step (3), the mass ratio of the adhesive, the ceramic material and the 1,3-propanediol cyclic carbonate is (58-62):(18-22):(18-22).

10. The method for preparing a battery separator according to claim 6, characterized in that, In step (4), the coating temperature is >80°C.

11. A lithium-ion battery, comprising a positive electrode, a negative electrode, and a separator spaced between the positive electrode and the negative electrode, characterized in that, The diaphragm is the diaphragm described in any one of claims 1-5.

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