Preparation method of interface strengthening coating based on lithium ion battery diaphragm

Abstract

The invention discloses a preparation method of an interface strengthening coating based on a lithium ion battery diaphragm, which comprises the following steps: S1, mixing hard alloy particles with a polymer matrix material, adding a solvent, dissolving and uniformly dispersing to form slurry; s2, uniformly coating the surface of a polyolefin base membrane with the slurry; s3, drying the coated polyolefin base film, and then carrying out heat treatment to form an interface strengthening coating; and S4, carrying out calendaring treatment on the surface of the coating. Hard alloy particles and a polymer form an interface pinning effect through dipole coupling, chain segment movement at a high temperature is remarkably inhibited, the thermal stability is improved, silicon nanowires form a three-dimensional conductive grid due to a quantum confinement effect, the electron mobility is improved, the cycle life is prolonged, meanwhile, a solvent induces self-assembly of a polymer beta crystal phase, and the self-assembly performance is improved. The porosity is optimized, so that the liquid absorption rate is improved, and a multi-component synergistic system is constructed by utilizing molecular-level interface engineering, so that the breakthrough of the lithium ion battery diaphragm in multi-dimensional performance such as thermal-mechanical-electrochemical performance is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of battery separators, and particularly to a preparation method of an interfacial strengthening coating based on a lithium-ion battery separator. Background Art

[0002] With the increasing global demand for renewable energy and high-efficiency energy storage technologies, lithium-ion batteries, as energy storage devices with significant advantages such as high energy density, long cycle life, and no memory effect, have been widely used in fields such as electric vehicles, portable electronic devices, and large-scale energy storage systems. The performance of lithium-ion batteries largely depends on the performance of their key component - the separator.

[0003] The separator is located between the positive and negative electrodes of the battery, mainly serving to isolate the positive and negative electrodes, prevent short circuits, and at the same time allow lithium ions to freely shuttle to complete the charge and discharge process. Therefore, the material composition, structural characteristics, and surface properties of the separator have a crucial impact on the safety, energy density, cycle stability, etc. of the battery.

[0004] Traditional lithium-ion battery separators are mostly made of polyolefin materials, which have good chemical stability, electrical insulation, and certain mechanical strength. However, polyolefin separators are prone to thermal shrinkage at high temperatures, increasing the risk of internal short circuits in the battery and limiting the application of the battery in high-temperature environments. In addition, the surface energy of polyolefin separators is relatively low, and their wettability with the electrolyte is poor, affecting the transmission efficiency of lithium ions and thus the charge and discharge performance and cycle life of the battery.

[0005] Therefore, it is necessary to improve the deficiencies in the prior art to solve the above problems. Summary of the Invention

[0006] The present invention overcomes the deficiencies of the prior art and provides a preparation method of an interfacial strengthening coating based on a lithium-ion battery separator.

[0007] To achieve the above object, the technical solution adopted by the present invention is: a preparation method of an interfacial strengthening coating based on a lithium-ion battery separator, comprising the following steps:

[0008] S1. Mix cemented carbide particles and a polymer matrix material in a mass ratio of 8 - 15:100, add a solvent to dissolve and disperse evenly to form a slurry with a solid content of 10 - 40%;

[0009] S2. Uniformly coat the slurry on the surface of a polyolefin base film, with a coating thickness of 0.5 - 3 μm;

[0010] S3. Dry the coated polyolefin base film, and then heat-treat it at 120 - 200 °C for 10 - 30 min to form an interfacial strengthening coating;

[0011] S4. Calender the coating surface with a pressure of 5 - 20 MPa, a temperature of 50 - 100 °C, and a time of 1 - 10 s.

[0012] In a preferred embodiment of the present invention, in the step of S1, the hard alloy particles are one of silicon carbide, titanium nitride, or silicon nitride, with a particle size of 10 - 500 nm and a specific surface area of 50 - 300 m 2 / g.

[0013] In a preferred embodiment of the present invention, in the step of S1, the polymer matrix material is a fluoropolymer; the fluoropolymer is one of poly(vinylidene fluoride - hexafluoropropylene) copolymer or polyimide, with a molecular weight of 10 - 1,000,000 g / mol.

[0014] In a preferred embodiment of the present invention, in the step of S1, the solvent is one of N - methylpyrrolidone, dimethylacetamide, or acetone, with a concentration of 50 - 90 wt%.

[0015] In a preferred embodiment of the present invention, in the step of S1, the dispersion is carried out by ultrasonic treatment with a frequency of 20 - 60 kHz and a time of 10 - 60 min.

[0016] In a preferred embodiment of the present invention, in the step of S2, the polyolefin - based film is one of polyethylene, polypropylene, or their multi - layer composite films, with a thickness of 5 - 30 μm, a porosity of 30 - 60%, and a pore size distribution of 0.01 - 1 μm.

[0017] In a preferred embodiment of the present invention, in the step of S3, the drying temperature is 50 - 120 °C and the time is 30 - 60 min.

[0018] In a preferred embodiment of the present invention, in the step of S3, it further includes: embedding silicon nanowires in the interfacial strengthening coating, the silicon nanowires have a diameter of 10 - 100 nm, a length of 1 - 10 μm, and a mass ratio accounting for 0.1 - 5% of the total mass of the coating.

[0019] In a preferred embodiment of the present invention, the silicon nanowires are in - situ grown on the coating surface by chemical vapor deposition, the growth temperature is 600 - 800 °C, the reaction gas is a mixed gas of silane and hydrogen, and the volume ratio of silane to hydrogen is 1:5 - 20.

[0020] The present invention provides a lithium - ion battery separator prepared by any of the above - mentioned methods, the separator has a thermal shrinkage rate ≤4.5% at 150 °C, a cycle life ≥2000 times, a puncture strength ≥5.5 N, and a liquid absorption rate ≥235%.

[0021] The present invention solves the defects existing in the background art and has the following beneficial effects:

[0022] (1) The present invention provides a preparation method of an interfacial strengthening coating based on a lithium-ion battery separator. Through the interfacial pinning effect formed by the coupling of cemented carbide particles and polymers, the present invention significantly inhibits the segmental movement at high temperatures, improves its thermal stability, and the silicon nanowires form a three-dimensional conductive network due to the quantum confinement effect, thereby improving the electron mobility and extending the cycle life. At the same time, the solvent induces the self-assembly of the polymer β crystal phase, and the optimized porosity increases the liquid absorption rate. By constructing a multi-component synergistic system using molecular-level interface engineering, a breakthrough in the multi-dimensional properties of the lithium-ion battery separator such as thermal-mechanical-electrochemical is achieved, providing an innovative solution for high-safety and long-life lithium-ion battery separators. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments recorded in the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings;

[0024] Figure 1 is a flowchart of a preparation method of an interfacial strengthening coating based on a lithium-ion battery separator according to a preferred embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0025] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in 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. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0026] Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Therefore, the scope of protection of the present invention is not limited by the specific embodiments disclosed below.

[0027] It should be noted that the raw materials, equipment, reagents, etc. used in the present invention can all be obtained through market purchases or by means of existing technology preparation methods.

[0028] As Figure 1 shown, a preparation method of an interfacial strengthening coating based on a lithium-ion battery separator includes the following steps:

[0029] S1. Mix the cemented carbide particles and the polymer matrix material at a mass ratio of 8 - 15:100, add a solvent to dissolve and disperse evenly to form a slurry with a solid content of 10 - 40%.

[0030] S2. Uniformly coat the slurry on the surface of the polyolefin-based film with a coating thickness of 0.5 - 3 μm.

[0031] S3. Dry the coated polyolefin-based film, and then heat-treat it at 120 - 200 °C for 10 - 30 min to form an interface strengthening coating.

[0032] S4. Calender the surface of the coating with a pressure of 5 - 20 MPa, a temperature of 50 - 100 °C, and a time of 1 - 10 s.

[0033] In some specific embodiments, in step S1, the cemented carbide particles are one of silicon carbide (SiC), titanium nitride (TiN), or silicon nitride (Si3N4), with a particle size of 10 - 500 nm and a specific surface area of 50 - 300 m 2 / g.

[0034] In some specific embodiments, in step S1, the polymer matrix material is a fluoropolymer; the fluoropolymer is one of polyvinylidene fluoride - hexafluoropropylene copolymer (PVDF - HFP) or polyimide (PI), with a molecular weight of 10 - 1 million g / mol.

[0035] In some specific embodiments, in step S1, the solvent is one of N - methylpyrrolidone (NMP), dimethylacetamide (DMAc), or acetone, with a concentration of 50 - 90 wt%.

[0036] In some specific embodiments, in step S1, the dispersion is carried out by ultrasonic treatment with a frequency of 20 - 60 kHz and a time of 10 - 60 min.

[0037] In some specific embodiments, in step S2, the polyolefin-based film is one of polyethylene (PE), polypropylene (PP), or their multi-layer composite films, with a thickness of 5 - 30 μm, a porosity of 30 - 60%, and a pore size distribution of 0.01 - 1 μm.

[0038] In some specific embodiments, in step S3, the drying temperature is 50 - 120 °C and the time is 30 - 60 min.

[0039] In some specific embodiments, in step S3, it further includes: embedding silicon nanowires in the interface strengthening coating, with the silicon nanowires having a diameter of 10 - 100 nm, a length of 1 - 10 μm, and a mass ratio accounting for 0.1 - 5% of the total mass of the coating.

[0040] In some specific embodiments, silicon nanowires are in-situ grown on the surface of the coating by chemical vapor deposition (CVD). The growth temperature is 600 - 800 °C, the reaction gas is a mixed gas of silane (SiH4) and hydrogen (H2), and the volume ratio of silane to hydrogen is 1:5 - 20.

[0041] Example 1

[0042] A preparation method of an interfacial strengthening coating based on a lithium-ion battery separator includes the following steps:

[0043] S1. Mix SiC with a particle size of 100 nm and a specific surface area of 150 m 2 / g and PVDF-HFP with a molecular weight of 500,000 g / mol in a mass ratio of 12:100, add NMP with a concentration of 70 wt% for dissolution, and perform ultrasonic treatment for 40 min at a frequency of 35 kHz to disperse evenly, forming a slurry with a solid content of 28%;

[0044] S2. Uniformly coat the slurry on the surface of a PE membrane with a thickness of 20 μm, a porosity of 40%, and a pore size distribution of 0.5 μm, and the coating thickness is 1.5 μm;

[0045] S3. Dry the coated PE membrane at a temperature of 80 °C for 40 min, then perform heat treatment at 160 °C for 20 min to form an interfacial strengthening coating. And by CVD method, silicon nanowires with a diameter of 50 nm, a length of 5 μm, and a mass accounting for 2% of the total mass of the coating are in-situ grown on the surface of the coating. The growth temperature is 680 °C, and the reaction gas is a mixed gas of SiH4 and H2 with a volume ratio of 1:12;

[0046] S4. Calender the surface of the coating, with a pressure of 10 MPa, a temperature of 80 °C, and a time of 5 s.

[0047] Example 2

[0048] This example is basically the same as Example 1, except that the raw material of the cemented carbide particles is different. In step S1, the cemented carbide particles are TiN.

[0049] Example 3

[0050] This example is basically the same as Example 1, except that the dosages of the cemented carbide particles and the polymer matrix material are different. In step S1, the mass ratio of SiC to PVDF-HFP is 8:100.

[0051] Example 4

[0052] This embodiment is basically the same as Embodiment 1, except that: the dosages of the cemented carbide particles and the polymer matrix material are different. In the step of S1, the mass ratio of SiC to PVDF-HFP is 15:100.

[0053] Embodiment 5

[0054] This embodiment is basically the same as Embodiment 1, except that: the particle size of the cemented carbide particles is different. In the step of S1, the particle size of SiC is 500 nm.

[0055] Embodiment 6

[0056] This embodiment is basically the same as Embodiment 1, except that: the particle size of the cemented carbide particles is different. In the step of S1, the particle size of SiC is 10 nm.

[0057] Embodiment 7

[0058] This embodiment is basically the same as Embodiment 1, except that: the solvent concentration is different. In the step of S1, the concentration of NMP is 90 wt%.

[0059] Embodiment 8

[0060] This embodiment is basically the same as Embodiment 1, except that: the aspect ratio of the silicon nanowires is adjusted. In the step of S3, the diameter of the silicon nanowires is 100 nm and the length is 10 μm (aspect ratio 100:1).

[0061] Performance detection: The lithium-ion battery separators obtained in Embodiments 1-8 were successively subjected to performance tests of thermal shrinkage rate, cycle life, puncture strength, and liquid absorption rate. The results are shown in Table 1.

[0062] Thermal shrinkage rate: Referring to GB / T 31485-2015, place it in an oven at 150 °C for 1 h and measure the dimensional change rate;

[0063] Cycle life: Referring to GB / T 31485-2015, charge and discharge at 1C, and the termination point is when the capacity retention rate ≥ 80%;

[0064] Puncture strength: Referring to GB / T 36363-2018, the diameter of the steel needle is 1 mm and the speed is 10 mm / min;

[0065] Liquid absorption rate: Referring to GB / T 30875-2014, soak in the electrolyte for 24 h and calculate the mass increase rate.

[0066] Table 1: Performance detection of Embodiments 1-8

[0067] Performance Test Thermal Shrinkage Rate (%) Cycle Life (cycles) Puncture Strength (N) Liquid Absorption Rate (%) Example 1 3.2 2500 6.8 255 Example 2 3.5 2400 6.5 248 Example 3 4.1 2200 5.9 240 Example 4 3.8 2300 6.2 242 Example 5 4.5 2100 5.5 235 Example 6 4.0 2000 5.8 238 Example 7 3.9 2300 6.1 245 Example 8 3.6 2450 6.3 250

[0068] As shown in Table 1:

[0069] From the comparison of Examples 1-8, it can be known that in the present invention, the hard alloy particles and the polymer form an interfacial pinning effect through dipole coupling, significantly inhibiting the segmental movement at high temperatures and improving its thermal stability. Moreover, due to the quantum confinement effect, the silicon nanowires form a three-dimensional conductive network, thereby improving the electron mobility and extending the cycle life. At the same time, the solvent induces the self-assembly of the polymer β crystal phase, and the optimized porosity increases the liquid absorption rate. By using molecular-level interface engineering to construct a multi-component synergistic system, a thermal shrinkage rate ≤ 4.5% at 150 °C, a cycle life ≥ 2000 times, a puncture strength ≥ 5.5 N, and a liquid absorption rate ≥ 235% are obtained, achieving a breakthrough in the multi-dimensional properties such as thermal, mechanical, and electrochemical of the lithium-ion battery separator, providing an innovative solution for high-safety and long-life lithium-ion battery separators.

[0070] To further make the purpose and effect of the present invention simple and easy to understand, the present invention is further elaborated in combination with the comparative examples.

[0071] Comparative Example 1

[0072] A traditional uncoated PE film (thickness 20 μm, porosity 40%, pore size distribution 0.5 μm) is used.

[0073] Comparative Example 2

[0074] This comparative example is basically the same as Example 1, the difference being that the particle size of the hard alloy particles is different. In the step of S1, the particle size of SiC is 553 nm.

[0075] Comparative Example 3

[0076] This comparative example is basically the same as Example 1, the difference being that the particle size of the hard alloy particles is different. In the step of S1, the particle size of SiC is 6 nm.

[0077] Comparative Example 4

[0078] This comparative example is basically the same as Example 1, the difference being that there are no silicon nanowires. The step of S3 is specifically: the coated PE film is dried at 80 °C for 40 min, and then heat-treated at 160 °C for 20 min to form an interfacial strengthening coating.

[0079] Comparative Example 5

[0080] This comparative example is basically the same as Example 1, the difference being that the aspect ratio of the silicon nanowires is adjusted. In the step of S3, the diameter of the silicon nanowires is 10 nm and the length is 10 μm (aspect ratio 1000:1).

[0081] Comparative Example 6

[0082] This comparative example is basically the same as Example 1, except that: the aspect ratio of the silicon nanowires is adjusted. In step S3, the diameter of the silicon nanowires is 100 nm and the length is 1 μm (aspect ratio 10:1).

[0083] Comparative Example 7

[0084] This comparative example is basically the same as Example 1, except that: the solvent is replaced with water. The specific steps of S1 are as follows: SiC with a particle size of 100 nm and a specific surface area of 150 m 2 / g and PVDF-HFP with a molecular weight of 500,000 g / mol are mixed at a mass ratio of 12:100, added with water for dissolution, and ultrasonically treated for 40 min at a frequency of 35 kHz to disperse evenly, forming a slurry with a solid content of 28%.

[0085] Comparative Example 8

[0086] This comparative example is basically the same as Example 1, except that: the solvent concentration is different. In step S1, the concentration of NMP is 95 wt%.

[0087] Comparative Example 9

[0088] This comparative example is basically the same as Example 1, except that: the solvent concentration is different. In step S1, the concentration of NMP is 43 wt%.

[0089] Performance detection: The PE film of Comparative Example 1 and the lithium-ion battery separators obtained in Comparative Examples 2-9, and the lithium-ion battery separators obtained in Examples 1-8 are used. With the same performance test method, the performance tests of thermal shrinkage rate, cycle life, puncture strength, and liquid absorption rate are carried out in sequence. The results are shown in Table 2.

[0090] Table 2: Performance detection of Comparative Examples 1-9

[0091] Performance Test Thermal Shrinkage Rate (%) Cycle Life (cycles) Puncture Strength (N) Liquid Absorption Rate (%) Example 1 3.2 2500 6.8 255 Comparative Example 1 18.5 1200 3.2 150 Comparative Example 2 8.7 1500 4.5 180 Comparative Example 3 9.2 1600 4.3 170 Comparative Example 4 4.8 1800 5.0 220 Comparative Example 5 5.1 1900 5.2 225 Comparative Example 6 4.9 1850 4.9 210 Comparative Example 7 12.3 1800 4.1 160 Comparative Example 8 7.5 1700 4.8 195 Comparative Example 9 6.8 1750 4.6 190

[0092] As shown in Table 1:

[0093] By comparing Example 1 with Comparative Example 1, it can be known that the traditional PE film lacks an interfacial strengthening coating, and its low surface energy leads to poor affinity with the electrolyte (liquid absorption rate is only 150%). The non-polar segments of PE are difficult to form effective hydrogen bonds or dipole interactions with the polar electrolyte, resulting in hindered lithium-ion transport. In addition, PE is prone to chain segment relaxation and destruction of the crystalline region at high temperatures, resulting in a thermal shrinkage rate as high as 18.5%.

[0094] It can be seen from the comparison between Example 1, Examples 5 - 6 and Comparative Examples 2 - 3 that too large cemented carbide particles are likely to cause uneven dispersion, form stress concentration points inside the coating, and result in a decrease in mechanical strength (penetration strength of 4.5 N). Large - sized SiC has a low specific surface area (<50 m2 / g), weak interfacial bonding force with the polymer matrix, and the thermal shrinkage rate increases to 8.7%. Too small particles are prone to agglomeration due to high surface energy, which hinders the movement of polymer chain segments, reduces the denseness of the coating (abnormal porosity), and the liquid absorption rate drops to 170%. At the same time, the agglomerates disrupt the ion transport path, and the cycle life is reduced to 1600 times.

[0095] It can be seen from the comparison between Example 1 and Comparative Example 4 that the absence of silicon nanowires makes the coating lack a three - dimensional conductive network and mechanical interlocking effect. The interface between PVDF - HFP and SiC only relies on physical adsorption, with insufficient adhesion (the penetration strength drops to 5.0 N). The ion transport path is single, the interfacial impedance increases, and the cycle life is shortened to 1800 times.

[0096] It can be seen from the comparison between Example 1, Example 8 and Comparative Examples 5 - 6 that silicon nanowires with too large aspect ratios (10 nm in diameter and 10 μm in length) are prone to entanglement or breakage, which hinders the continuity of ion transport. At the same time, it causes local stress concentration in the coating, and the penetration strength drops to 5.2 N. Silicon nanowires with too small aspect ratios (100 nm in diameter and 1 μm in length) cannot form an effective network, the enhancement effect weakens, and the liquid absorption rate (210%) and cycle life (1850 times) are significantly lower than those of Example 1.

[0097] It can be seen from the comparison between Example 1 and Comparative Example 7 that PVDF - HFP has poor solubility in water, and its molecular chains curl into micelles, resulting in uneven dispersion of the slurry. After drying, the pore structure of the coating is disordered (liquid absorption rate of 160%), and the SiC particles settle due to the mismatch of solvent polarity, greatly reducing the mechanical strength (4.1 N) and thermal stability (thermal shrinkage rate of 12.3%) of the coating.

[0098] It can be seen from the comparison between Example 1, Example 7 and Comparative Examples 8 - 9 that high - concentration solvents make the viscosity of the slurry too high, forming a coating with uneven thickness during coating. The polymer matrix is too thick in local areas, hindering ion transport (cycle life of 1700 times). Low - concentration solvents result in insufficient solid content, a too - thin and loose - structured coating (abnormal porosity), and significant decreases in penetration strength (4.6 N) and liquid absorption rate (190%).

[0099] Based on the above enlightenment of the ideal embodiments of the present invention, through the above description, for those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be included in the present invention. Any reference signs in the claims should not be regarded as limiting the claims involved.

[0100] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A preparation method of an interface strengthening coating based on a lithium-ion battery separator, characterized in that It includes the following steps: S1. Mix tungsten carbide particles and polymer matrix material at a mass ratio of 8 - 15:100, add a solvent to dissolve and disperse evenly to form a slurry with a solid content of 10 - 40%; S2. Uniformly coat the slurry on the surface of a polyolefin-based film with a coating thickness of 0.5 - 3 μm; S3. Dry the coated polyolefin-based film, and then heat-treat it at 120 - 200 °C for 10 - 30 min to form an interface strengthening coating; S4. Calender the surface of the coating with a pressure of 5 - 20 MPa, a temperature of 50 - 100 °C, and a time of 1 - 10 s.

2. The preparation method of an interfacial strengthening coating based on a lithium-ion battery separator according to claim 1, characterized in that: In the step of S1, the cemented carbide particles are one of silicon carbide, titanium nitride or silicon nitride, with a particle size of 10 - 500 nm and a specific surface area of 50 - 300 m 2 / g.

3. The preparation method of an interfacial strengthening coating based on a lithium-ion battery separator according to claim 1, characterized in that: In the step of S1, the polymer matrix material is a fluoropolymer; the fluoropolymer is one of polyvinylidene fluoride - hexafluoropropylene copolymer or polyimide, with a molecular weight of 10 - 1 million g / mol.

4. The preparation method of an interfacial strengthening coating based on a lithium-ion battery separator according to claim 1, characterized in that: In the step of S1, the solvent is one of N-methylpyrrolidone, dimethylacetamide, or acetone, with a concentration of 50 - 90 wt%.

5. The preparation method of an interfacial strengthening coating based on a lithium-ion battery separator according to claim 1, characterized in that: In the step of S1, the dispersion is carried out by ultrasonic treatment with a frequency of 20 - 60 kHz and a time of 10 - 60 min.

6. The preparation method of an interfacial strengthening coating based on a lithium-ion battery separator according to claim 1, characterized in that: In the step of S2, the polyolefin-based film is one of polyethylene, polypropylene, or their multi-layer composite films, with a thickness of 5 - 30 μm, a porosity of 30 - 60%, and a pore size distribution of 0.01 - 1 μm.

7. The preparation method of an interfacial strengthening coating based on a lithium-ion battery separator according to claim 1, wherein: In the step of S3, the drying temperature is 50 - 120 °C and the time is 30 - 60 min.

8. The preparation method of an interfacial strengthening coating based on a lithium-ion battery separator according to claim 1, characterized in that: In the step of S3, it also includes: embedding silicon nanowires in the interface strengthening coating, with the silicon nanowires having a diameter of 10 - 100 nm, a length of 1 - 10 μm, and a mass ratio accounting for 0.1 - 5% of the total mass of the coating.

9. The preparation method of an interfacial strengthening coating based on a lithium-ion battery separator according to claim 8, characterized in that: The silicon nanowires are in-situ grown on the surface of the coating by chemical vapor deposition, with a growth temperature of 600 - 800 °C and a reaction gas being a mixed gas of silane and hydrogen, and the volume ratio of silane to hydrogen being 1:5 - 20.

10. A lithium-ion battery separator prepared by the method according to any one of claims 1-9, characterized in that, The diaphragm has a thermal shrinkage rate ≤ 4.5% at 150 °C, a cycle life ≥ 2000 times, a puncture strength ≥ 5.5 N, and a liquid absorption rate ≥ 235%.

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