Novel diaphragm of secondary battery and preparation method of novel diaphragm

Abstract

The invention relates to a secondary battery, in particular to a novel diaphragm of a lithium battery and a preparation method of the novel diaphragm, the novel secondary battery is formed by combining organic salt and metal oxide, and different purposes of high conductivity, flame retardance, puncture resistance and the like can be achieved.

Description

Technical Field

[0001] This invention relates to a novel separator for secondary batteries, particularly lithium batteries, and its preparation method. Background Technology

[0002] In recent years, the global energy structure has been rapidly transitioning towards cleaner energy sources. As a core energy storage medium, lithium-ion batteries have seen their market size expand continuously, driven by the widespread adoption of new energy vehicles, the large-scale application of new energy storage systems, and the iterative development of consumer electronics technology. According to industry research data, the global lithium-ion battery market exceeded US$70 billion in 2023 and is projected to continue expanding at a compound annual growth rate of over 25% over the next five years, reaching a market size of US$278 billion by 2029.

[0003] However, safety accidents caused by thermal runaway in lithium batteries have become a key bottleneck restricting the sustainable development of the industry. As the core safety barrier of the battery system, the thermodynamic stability of the separator directly determines the failure threshold of the battery under extreme conditions. Although the current mainstream polyolefin (PE / PP) based separator has excellent processing adaptability, its intrinsic thermal properties pose significant safety hazards: the softening point of the material is in the critical range of 130℃ (PE) and 160℃ (PP), and it exhibits more than 20% irreversible in-plane shrinkage under thermal shock exceeding its softening point temperature. This thermally induced deformation will directly cause short circuits in the electrode phase contact, thereby activating a chain thermal runaway reaction. The current technical route in the industry mainly adopts ceramic coating process for heat resistance modification. Although this solution can improve the intrinsic heat resistance of the separator, its protection mechanism has a fundamental defect—when the battery is subjected to abuse conditions such as mechanical puncture, overcharge / over-discharge or external thermal shock, the coating structure cannot effectively block the thermal runaway process, let alone suppress the secondary damage effect caused by thermal propagation. Summary of the Invention

[0004] Therefore, one of the objectives of this invention is to address the difficulties of existing separators in effectively blocking thermal runaway processes and suppressing thermal propagation by constructing a multifunctional flame-retardant and heat-resistant coating on the surface of traditional separators, thereby significantly improving the thermal safety performance of batteries.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: A novel diaphragm includes a base membrane and a coating; the coating is located on at least one side surface of the base membrane; the base membrane includes a polymer base membrane; and the coating includes an organic salt and a metal oxide.

[0006] Preferably, the organic salt includes melamine cyanurate (MCA) and / or melamine polyphosphate (MPP); the metal oxide includes at least one of Al2O3, MgO, ZrO2, and TiO2.

[0007] Preferably, the coating further includes a solid additive, which includes at least one of SiO2 and BaTiO3; the average particle size of the solid additive is 5 nm to 100 nm.

[0008] Preferably, the average particle size of the metal oxide is from 0.05 μm to 20 μm.

[0009] Preferably, the mass ratio of the organic salt to the metal oxide is 1:0.05 to 1:99.

[0010] Preferably, the novel diaphragm has a needle puncture resistance greater than or equal to 400 gf.

[0011] Preferably, the base film is in the form of a single layer, a double layer, or a multilayer, and when the base film is in the form of a double layer or a multilayer, its material includes the same or different materials.

[0012] Preferably, the average particle size of the organic salt is 0.3 μm to 20 μm.

[0013] Preferably, the thickness of the novel diaphragm is 3 μm to 42 μm; and / or, the thickness of the base film is 2 μm to 40 μm; and / or, the thickness of the coating is 0.5 μm to 9 μm.

[0014] The present invention also provides a method for manufacturing a novel diaphragm, comprising the following steps: a coating slurry preparation step: adding solid materials and a binder to a dispersion medium to form a coating slurry, wherein the solid materials include organic salts and metal oxides, the organic salts including melamine cyanurate (MCA) and / or melamine polyphosphate (MPP), and the metal oxides including at least one of Al2O3, MgO, ZrO2, and TiO2; and a coating step: coating the coating slurry onto at least one side surface of a base membrane to form a novel diaphragm.

[0015] Preferably, the slurry solids content in the coating slurry is 5% to 50%; and / or, the slurry viscosity in the coating slurry is 10cp to 1000cp; and / or, the coating slurry D99 is 3μm to 6μm.

[0016] Preferably, the solid material further includes a solid additive, which includes at least one of SiO2 and BaTiO3, and the average particle size of the solid additive is 5 nm to 100 nm.

[0017] Preferably, the coating slurry preparation step includes: a first step: adding the solid material and dispersant to the dispersion medium to form a first slurry; and a second step: adding the binder and wetting agent to the first slurry to form the coating slurry.

[0018] Preferably, the dispersant is at least one selected from polymethacrylate, polyacrylamide, polyacrylate, polyacrylic acid and its salts, triethylhexylphosphate, sodium dodecyl sulfate, fatty acid polyethylene glycol ester, sodium hexametaphosphate and methylpentanol.

[0019] Preferably, the wetting agent comprises at least one selected from ethanol, propylene glycol, glycerin, polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, fatty acid ester sulfate, and vinyltriethoxysilane.

[0020] Preferably, the manufacturing method further includes a drying step: drying the novel diaphragm to form a dried novel diaphragm. Attached Figure Description

[0021] Figure 1 This is a flowchart of the preparation method in the first embodiment; Figure 2 This is a flowchart of the preparation method in the second embodiment. Detailed Implementation

[0022] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0023] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0025] According to one objective of the present invention, a novel diaphragm is provided, comprising a base membrane and a coating; the coating is located on at least one surface of the base membrane; the base membrane comprises a polymer base membrane; and the coating comprises an organic salt and a metal oxide. The coating is obtained by applying a coating slurry to at least one surface of the base membrane and then drying it.

[0026] In a preferred embodiment, the organic salt includes melamine cyanurate (MCA) and / or melamine polyphosphate (MPP); the metal oxide includes at least one of Al2O3, MgO, ZrO2, and TiO2; preferably Al2O3.

[0027] In a preferred embodiment, the coating further includes a solid additive, which includes at least one of SiO2 and BaTiO3; the average particle size of the solid additive is 5 nm to 100 nm, preferably, the average particle size of the solid additive can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm.

[0028] In a preferred embodiment, the average particle size of the metal oxide is from 0.05 μm to 20 μm; preferably from 0.05 μm to 2 μm. More preferably, the average particle size of the metal oxide can be 0.1 μm, 0.3 μm, 0.5 μm, 1 μm, 5 μm, 10 μm, or 15 μm.

[0029] In a preferred embodiment, the mass ratio of the organic salt to the metal oxide is 1:0.05 to 1:99; preferably 1:0.05 to 1:20.

[0030] In a preferred embodiment, the novel diaphragm has a needle puncture resistance greater than or equal to 400 gf.

[0031] In a preferred embodiment, the base film is in the form of a single layer, a double layer, or a multilayer, and when the base film is in the form of a double layer or a multilayer, its material includes the same or different materials.

[0032] Preferably, the average particle size of the organic salt is 0.3 μm to 20 μm; more preferably, it is 0.3 μm to 10 μm; specifically, the average particle size of the organic salt is 0.5 μm, 1 μm, 2 μm, 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 11 μm or 15 μm.

[0033] In a preferred embodiment, the thickness of the novel diaphragm is 3 μm to 42 μm; and / or, the thickness of the base film is 2 μm to 40 μm; and / or, the thickness of the coating is 0.5 μm to 9 μm.

[0034] This invention also provides a novel method for manufacturing a diaphragm, the steps of which include: Figure 1As shown, the coating slurry preparation steps are as follows: A solid material and a binder are added to a dispersion medium to form a coating slurry; the coating step involves coating the coating slurry onto at least one side surface of a base film to form a novel diaphragm. The solid material comprises an organic salt and a metal oxide, wherein the organic salt comprises melamine cyanurate (MCA) and / or melamine polyphosphate (MPP), and the metal oxide comprises at least one of Al₂O₃, MgO, ZrO₂, and TiO₂.

[0035] In a preferred embodiment, the slurry solids content in the coating slurry is 5% to 50%; and / or, the slurry viscosity in the coating slurry is 10cp to 1000cp; and / or, the coating slurry D99 is 3μm to 6μm.

[0036] In a preferred embodiment, the solid material further includes a solid additive, which includes at least one of SiO2 and BaTiO3, and the average particle size of the solid additive is 5 nm to 100 nm.

[0037] In a preferred embodiment, the coating slurry preparation step includes: a first step: adding the solid material and dispersant to the dispersion medium to form a first slurry; and a second step: adding the binder and wetting agent to the first slurry to form the coating slurry.

[0038] In a preferred embodiment, the dispersant is at least one selected from polymethacrylate, polyacrylamide, polyacrylate, polyacrylic acid and its salts, triethylhexylphosphate, sodium dodecyl sulfate, fatty acid polyethylene glycol ester, sodium hexametaphosphate and methylpentanol.

[0039] In a preferred embodiment, the wetting agent includes at least one selected from ethanol, propylene glycol, glycerin, polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, fatty acid ester sulfate, and vinyltriethoxysilane.

[0040] In a preferred embodiment, after the coating step, the manufacturing method further includes a drying step: drying the novel diaphragm to form a dried novel diaphragm.

[0041] In a preferred embodiment, the method for manufacturing the novel diaphragm includes the following steps, such as... Figure 2 As shown, the first step is to add the solid material and dispersant to the dispersion medium to form a first slurry; the second step is to add the binder and wetting agent to the first slurry to form a coating slurry; the coating slurry is then applied to at least one side surface of the base film to form a novel diaphragm.

[0042] The present invention will be further described in detail below with reference to several embodiments, but this is not intended to limit the scope of protection of the present invention.

[0043] The base film was selected from porous polyethylene (PE) prepared by Shanghai Enjie, model ND9; MCA CAS number: 37640-57-6, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; MPP CAS number: 15541-60-3, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; polymethyl methacrylate, purchased from Jinzhou Shengda Chemical Co., Ltd.; polyacrylamide CAS number: 25085-02-3, purchased from Jiangsu Puleisi Biotechnology Co., Ltd.; methyl pentanol CAS number: 42072-39-9, purchased from Shanghai Maclean Biochemical Technology Co., Ltd.; vinyltriethoxysilane CAS number: 78-08-0, purchased from Jiangsu Bosite Chemical Technology Co., Ltd.

[0044] Example 1 This embodiment provides a diaphragm, which includes a base membrane and coatings applied to both sides of the base membrane.

[0045] The base membrane is made of 9 μm thick porous polyethylene (PE), and the coatings on both sides of the base membrane are 2 μm thick. The total thickness of the diaphragm is 13 μm.

[0046] The raw materials for preparing the coating, by mass, include 90 parts of MCA particles (D50 of 0.8 μm), 10 parts of Al2O3 (D50 of 0.5 μm), 6 parts of polymethacrylate, 1 part of dispersant (methylpentanol), and 0.1 parts of wetting agent (vinyltriethoxysilane).

[0047] The preparation method of the diaphragm includes: S1: According to the above-mentioned amount of raw materials, add MCA particles, Al2O3 particles and dispersant to 300 parts of deionized water, and mechanically stir at 2000 rpm for 1 hour to obtain the first slurry, i.e., stable dispersion; ball mill the first slurry in a ball mill jar to disperse it evenly, the ball milling rate is 700 rpm and the ball milling time is 1.5 hours to obtain the ball-milled first slurry.

[0048] S2: Filter the first slurry after ball milling, add polymethyl methacrylate and wetting agent to the filtered first slurry, and mechanically stir for 1 h at a stirring speed of 500 rpm to obtain a coating slurry; the slurry solid content in the coating slurry is 20%, and the slurry viscosity in the coating slurry is 80 cp.

[0049] S3: The above coating slurry is evenly coated on both sides of the base film on a coating machine and dried at 60°C for 5 minutes to obtain a diaphragm with a coating on both sides of the base film.

[0050] Example 1.1 The difference between this embodiment and Embodiment 1 is that: the MCA particles are changed to 70 parts, and the Al2O3 is changed to 30 parts; the viscosity of the coating slurry is 63 cp.

[0051] Example 1.2 The difference between this embodiment and Embodiment 1 is that: the MCA particles are changed to 30 parts, and the Al2O3 is changed to 70 parts; the viscosity of the coating slurry is 64 cp.

[0052] Example 1.3 The difference between this embodiment and Embodiment 1 is that: the MCA particles are changed to 10 parts, and the Al2O3 is changed to 90 parts; the viscosity of the coating slurry is 66 cp.

[0053] Example 2 The difference between this embodiment and Embodiment 1 is that: 10 parts Al2O3 are replaced with 10 parts MgO (average particle size is 0.3 μm); 6 parts polymethyl methacrylate are replaced with 7 parts styrene-butadiene rubber binder; the slurry solid content in the coating slurry is 25%; and the slurry viscosity in the coating slurry is 60 cp.

[0054] Example 2.1 The difference between this embodiment and Embodiment 2 is that the MCA particles are changed to 70 parts and the MgO is changed to 30 parts; the viscosity of the coating slurry is 66 cp.

[0055] Example 2.2 The difference between this embodiment and Embodiment 2 is that the MCA particles are changed to 30 parts and the MgO is changed to 70 parts; the viscosity of the coating slurry is 63 cp.

[0056] Example 2.3 The difference between this embodiment and Embodiment 2 is that the MCA particles are changed to 10 parts and the MgO is changed to 90 parts; the viscosity of the coating slurry is 70 cp.

[0057] Example 3 The difference between this embodiment and Embodiment 1 is that: MCA particles with an average particle size of 0.5 μm are selected, and 10 parts of Al2O3 are replaced with 10 parts of TiO2 (with an average particle size of 0.5 μm); the slurry solid content in the coating slurry is 24%, and the slurry viscosity in the coating slurry is 120 cP.

[0058] Example 3.1 The difference between this embodiment and Embodiment 3 is that the MCA particles are changed to 70 parts and the TiO2 is changed to 30 parts; the viscosity of the coating slurry is 135 cP.

[0059] Example 3.2 The difference between this embodiment and Embodiment 1 is that the MCA particles are changed to 30 parts and the TiO2 is changed to 70 parts; the viscosity of the slurry in the coating slurry is 150 cP.

[0060] Example 3.3 The difference between this embodiment and Embodiment 1 is that: the MCA particles are changed to 10 parts, and the TiO2 is changed to 90 parts; the viscosity of the slurry in the coating slurry is 165 cP.

[0061] Example 4 The difference between this embodiment and Example 1 is that: 10 parts Al2O3 are replaced with 10 parts ZrO2 (average particle size is 0.5 μm); the dispersant is replaced with 1.5 parts, and the polymethyl methacrylate is replaced with 7 parts; the slurry solid content in the coating slurry is 24%, and the slurry viscosity in the coating slurry is 25 cP.

[0062] Example 4.1 The difference between this embodiment and Embodiment 1 is that: the MCA particles are changed to 70 parts, and the ZrO2 is changed to 30 parts; the viscosity of the slurry in the coating slurry is 110 cP.

[0063] Example 4.2 The difference between this embodiment and embodiment 4 is that the MCA particles are changed to 30 parts and the ZrO2 is changed to 70 parts; the viscosity of the slurry in the coating slurry is 180 cP.

[0064] Example 4.3 The difference between this embodiment and embodiment 4 is that the MCA particles are changed to 10 parts and the ZrO2 is changed to 90 parts; the viscosity of the slurry in the coating slurry is 250 cP.

[0065] Example 5 The difference between this embodiment and Embodiment 1 is as follows: 80 parts of MCA particles with an average particle size of 1 μm are selected; 10 parts of Al2O3 are replaced with 10 parts of ZrO2 (D50 is 0.5 μm); 10 parts of SiO2 (D50 is 0.5 μm) are added; 0.5 parts of dispersant are replaced with 1.5 parts; 5 parts of polymethyl methacrylate are replaced with 7 parts; the slurry solid content in the coating slurry is 24%; and the slurry viscosity in the coating slurry is 280 cP.

[0066] Example 5.1 The difference between this embodiment and Embodiment 5 is that the MCA particles are changed to 70 parts and the ZrO2 is changed to 20 parts; the viscosity of the coating slurry is 320 cP.

[0067] Example 5.2 The difference between this embodiment and embodiment 5 is that the MCA particles are changed to 30 parts and the ZrO2 is changed to 60 parts; the viscosity of the slurry in the coating slurry is 380 cP.

[0068] Example 5.3 The difference between this embodiment and embodiment 5 is that the MCA particles are changed to 10 parts and the ZrO2 is changed to 80 parts; the viscosity of the slurry in the coating slurry is 420 cP.

[0069] Example 6 The difference between this embodiment and Embodiment 1 is that the slurry solid content in the coating slurry is 22%, and the slurry viscosity in the coating slurry is 28 cP.

[0070] Example 7 The difference between this embodiment and Embodiment 1 is that the slurry solid content in the coating slurry is 24%, and the slurry viscosity in the coating slurry is 35 cP.

[0071] Example 8 The difference between this embodiment and Embodiment 1 is that the slurry solid content in the coating slurry is 26%, and the slurry viscosity in the coating slurry is 120 cP.

[0072] Example 9 The difference between this embodiment and Embodiment 1 is that the slurry solid content in the coating slurry is 28%, and the slurry viscosity in the coating slurry is 180 cP.

[0073] Example 10 The difference between this embodiment and Embodiment 1 is that: the MCA particles are replaced with 90 parts MPP (D50 is 1 μm); the slurry solids content in the coating slurry is 24%, and the slurry viscosity in the coating slurry is 105 cP.

[0074] Example 11 The difference between this embodiment and embodiment 3.1 is that: the MCA particles are replaced with 70 parts of MPP (D50 is 1 μm); the slurry solid content in the coating slurry is 24%; and the slurry viscosity in the coating slurry is 140 cP.

[0075] Example 12 The difference between this embodiment and embodiment 4.2 is that: the MCA particles are replaced with 70 parts of MPP (D50 is 1 μm); the slurry solid content in the coating slurry is 24%; and the slurry viscosity in the coating slurry is 220 cP.

[0076] Comparative Example 1 The difference between this comparative example and Example 1 is that the raw materials for preparing the coating include 100 parts of MCA particles (average particle size of 1 μm), 5 parts of polymethyl methacrylate, 0.5 parts of polyacrylamide and 0.5 parts of methylpentanol as dispersants, and 0.1 parts of vinyltriethoxysilane as a wetting agent; the slurry solids content in the coating slurry is 20%, and the slurry viscosity in the coating slurry is 15 cP.

[0077] Comparative Example 2 The difference between this comparative example and Example 1 is that the solid material is replaced with 100 parts of Al2O3 particles (average particle size of 0.8 μm), 1 part of polymethyl methacrylate, 0.5 parts of polyacrylamide and 0.5 parts of methylpentanol as dispersants, and 0.1 parts of vinyltriethoxysilane as a wetting agent. Both sides of the base film of this comparative example are coated with the slurry prepared from the aforementioned materials. The solid content of the slurry is 20%, and the viscosity of the slurry is 20 cP.

[0078] Comparative Example 3 The difference between this comparative example and Example 2 is that the raw materials for preparing the coating include 100 parts of MgO (average particle size of 0.3 μm); the slurry solid content in the coating slurry is 25%; and the slurry viscosity in the coating slurry is 25 cP.

[0079] Comparative Example 4 The difference between this comparative example and Example 3 is that the raw materials for preparing the coating include 100 parts of TiO2 (average particle size of 0.5 μm); the slurry solid content in the coating slurry is 24% and the slurry viscosity in the coating slurry is 30 cP.

[0080] Comparative Example 5 The difference between this comparative example and Example 4 is that the raw materials for preparing the coating include 100 parts of ZrO2 (average particle size of 0.5 μm); the slurry solid content in the coating slurry is 24%, and the slurry viscosity in the coating slurry is 40 cP.

[0081] Comparative Example 6 The difference between this comparative example and Example 1 is that the slurry solid content in the coating slurry is 18%, and the slurry viscosity in the coating slurry is 10 cP.

[0082] Comparative Example 7 The difference between this comparative example and Example 1 is that the slurry solid content in the coating slurry is 30%, and the slurry viscosity in the coating slurry is 850 cP.

[0083] Comparative Example 8 The difference between this comparative example and Example 1 is that the raw materials for preparing the coating include 5 parts of MCA particles and 95 parts of Al2O3; the slurry solid content in the coating slurry is 24%, and the slurry viscosity in the coating slurry is 90 cP.

[0084] Comparative Example 9 The difference between this comparative example and Example 1 is that the raw materials for preparing the coating include 100 parts of MPP (D50 is 1); the slurry solid content in the coating slurry is 24%, and the slurry viscosity in the coating slurry is 95 cP.

[0085] The diaphragm performance testing method is as follows: Heat shrinkage rate: The diaphragm was cut into multiple 120mm × 100mm (length × width) pieces along the longitudinal (MD) and transverse (TD) directions. Two sheets of A4 paper were placed over the top and bottom surfaces of the diaphragm, and the pieces were placed in an oven at 180°C for 1 hour. The shrinkage rate in each direction was measured, and the shrinkage percentage was calculated. The shrinkage rate values ​​in Table 1 are based on the average values ​​obtained from three measurements in the MD and TD directions at 180°C.

[0086] Particle size test: The particle size of the coating slurry was tested using a Malvern MS3000 laser particle size analyzer, and the test results are also presented in Table 1.

[0087] Table 1

[0088]

[0089]

[0090] Table 1 reveals the particle size of the coating slurry and its longitudinal (MD) and transverse (TD) shrinkage at 180°C under different parameters. The data in Table 1 show that as the metal oxide content in the coating slurry increases, the dispersion difficulty of the slurry increases accordingly, manifested as an upward trend in the particle size (D99) of the solid particles in the slurry. Under the same test conditions, the thermal shrinkage rate of the diaphragm in both the longitudinal (MD) and transverse (TD) directions significantly decreases with increasing metal oxide content. Furthermore, in Comparative Example 7, due to the excessively high solid content (30%) in the slurry, the slurry viscosity was too high to achieve uniform coating, thus failing to obtain effective diaphragm samples and subsequent performance data. Thermal shrinkage rate is a key indicator for evaluating the high-temperature dimensional stability of the diaphragm; the lower the value, the stronger the dimensional retention ability of the diaphragm under thermal abuse conditions, and the more effectively it can avoid safety hazards such as internal short circuits caused by diaphragm shrinkage.

[0091] Puncture strength: Refer to the standard GBT36363-2018; thickness is measured using a Malmite film thickness gauge.

[0092] Flame retardancy test: The new diaphragm was cut into multiple 127mm × 12.7mm (length × width) specimens along the longitudinal (MD) and transverse (TD) directions, and the test was conducted in a non-ventilated test chamber. The upper end of the specimen was clamped with a fixture on a support, keeping the longitudinal axis of the specimen perpendicular. The lower end of the specimen was 9.5mm ± 2mm from the nozzle of the Bunsen burner. The Bunsen burner was lit and adjusted to produce a blue flame 19mm ± 5mm high. The Bunsen burner flame was placed at the lower end of the specimen and ignited for 10 seconds. Then the flame was removed, and the burning time of the specimen was recorded (no burning was recorded as 0 seconds). At the same time, the above specimens were tested according to the standard GBT40302-2021 to obtain the burning time T. Both flame retardancy tests were repeated three times for each group of specimens, and the average value was taken.

[0093] Table 2

[0094]

[0095] As shown in Table 2 above, the experimental data further confirms that the combination of organic salts and metal oxides is the key to optimizing the overall performance of the diaphragm. While single-component systems may excel in a particular performance aspect, none can simultaneously meet the comprehensive requirements of high-efficiency flame retardancy, high mechanical strength, and excellent thermal stability. Furthermore, the proportion of metal oxides is not simply a matter of "the more the better." As shown in Table 2, as the content of metal oxides continuously increases, the flame retardant effect of the diaphragm does not continuously improve; instead, it decreases after exceeding a certain critical ratio, and may even lose its flame retardant ability. Conversely, when the proportion of organic salts is too high, although the flame retardant performance is excellent, the puncture resistance and heat resistance decrease. Therefore, the core of this invention lies in precisely controlling the mass ratio of organic salts to metal oxides to establish a synergy between "gas-phase flame retardancy" and "solid-phase reinforcement," thereby accurately designing the final performance of the diaphragm. This composite system successfully solves the technical bottleneck of traditional solutions where flame retardant efficiency, mechanical strength, and thermal stability are difficult to balance, constructing a functionally complementary and synergistically effective "gas-solid dual-phase" protection system.

[0096] Specifically, the organic salts (such as MCA and MPP) serve as the main gas-phase flame retardant, rapidly decomposing and releasing a large amount of non-flammable gas in the early stages of thermal runaway. By diluting oxygen and isolating combustibles, they achieve the ultimate flame retardant effect of "zero combustion time" in many embodiments. Meanwhile, the metal oxides (such as Al2O3, TiO2, ZrO2, etc.) serve as a physical reinforcing skeleton, significantly improving the mechanical properties of the membrane (such as puncture resistance generally increasing to over 550 gf) and high-temperature dimensional stability (such as reducing the thermal shrinkage rate at 180℃ to below 2.0%).

[0097] Of particular note is that this invention achieves "customizable" membrane performance by precisely controlling the ratio of organic salt to metal oxide. Within a wide range of organic salt to metal oxide mass ratios from 90:10 to 30:70, the membrane maintains excellent flame retardancy with "zero combustion," while its mechanical and thermal properties systematically improve with increasing oxide content. This provides unprecedented design flexibility to meet battery safety requirements in different application scenarios.

[0098] Furthermore, by introducing nanoscale solid additives (such as SiO2 and BaTiO3), this invention achieves a further leap in performance. Nanoparticles, with their high specific surface area and surface activity, can form a denser microstructure in the coating, not only constructing a more effective "ceramic armor" at high temperatures, but also generating a super-synergistic effect with the gas-phase flame-retardant mechanism of organic salts. This allows the membrane to simultaneously achieve excellent comprehensive performance of "zero combustion," high puncture strength (>600 gf), and low thermal shrinkage even at extremely low organic salt content (e.g., 30 parts).

[0099] In summary, this invention is not a simple superposition of components, but rather a creative system design that successfully integrates rapid chemical flame retardancy with robust physical protection, providing a next-generation high-safety lithium battery separator solution with comprehensive performance far exceeding that of a single component and flexible design capabilities, which is of great significance for promoting the development of battery safety technology.

[0100] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A novel diaphragm, characterized in that, Including base film and coating; The coating is located on at least one side surface of the base film; The base film includes a polymer base film; and The coating comprises organic salts and metal oxides.

2. The novel diaphragm according to claim 1, characterized in that, The organic salt includes melamine cyanurate (MCA) and / or melamine polyphosphate (MPP); the metal oxide includes at least one of Al2O3, MgO, ZrO2, and TiO2.

3. The novel diaphragm according to claim 1, characterized in that, The coating also includes a solid additive, which includes at least one of SiO2 and BaTiO3, and the average particle size of the solid additive is 5 nm to 100 nm.

4. The novel diaphragm according to claim 1, characterized in that, The average particle size of the metal oxide is from 0.05 μm to 20 μm.

5. The novel diaphragm according to claim 1, characterized in that, The mass ratio of the organic salt to the metal oxide is from 1:0.05 to 1:

99.

6. The novel diaphragm according to claim 1, characterized in that, The novel diaphragm has a needle puncture resistance greater than or equal to 400 gf.

7. The novel diaphragm according to claim 1, characterized in that, The base film can be in the form of a single layer, a double layer, or a multilayer, and when the base film is in the form of a double layer or a multilayer, its material can be the same or different materials.

8. The novel diaphragm according to claim 1, characterized in that, The average particle size of the organic salt is 0.3 μm to 20 μm.

9. The novel diaphragm according to claim 1, characterized in that, The thickness of the novel diaphragm is 3 μm to 42 μm; and / or, the thickness of the base film is 2 μm to 40 μm; and / or, the thickness of the coating is 0.5 μm to 9 μm.

10. A method for manufacturing a novel diaphragm, comprising the following steps: Coating slurry preparation steps: Solid materials and binders are added to a dispersion medium to form a coating slurry, wherein the solid materials include organic salts and metal oxides, the organic salts include melamine cyanurate (MCA) and / or melamine polyphosphate (MPP), and the metal oxides include at least one selected from Al2O3, MgO, ZrO2, and TiO2; and Coating step: Coating slurry is applied to at least one side of the base membrane to form a novel diaphragm.

11. The method for manufacturing the novel diaphragm according to claim 10, characterized in that, The slurry has a solids content of 5% to 50%; and / or, the slurry viscosity is 10cp to 1000cp; and / or, the slurry D99 is 3μm to 6μm.

12. The method for manufacturing the novel diaphragm according to claim 10, characterized in that, The solid material further includes solid additives, which include at least one of SiO2 and BaTiO3, and the average particle size of the solid additives is 5 nm to 100 nm.

13. The method for manufacturing the novel diaphragm according to claim 10, characterized in that, The steps for preparing the coating slurry include: First step: Add the solid material and dispersant to the dispersion medium to form a first slurry; and The second step is to add the binder and wetting agent to the first slurry to form the coating slurry.

14. The method for manufacturing the novel diaphragm according to claim 13, characterized in that, The dispersant is at least one of polymethacrylate, polyacrylamide, polyacrylate, polyacrylic acid and its salts, triethylhexylphosphate, sodium dodecyl sulfate, fatty acid polyethylene glycol ester, sodium hexametaphosphate and methylpentanol.

15. The method for manufacturing the novel diaphragm according to claim 13, characterized in that, The wetting agent includes at least one of ethanol, propylene glycol, glycerin, polyoxyethylene alkylphenol ether, polyoxyethylene fatty alcohol ether, fatty acid ester sulfate, and vinyltriethoxysilane.

16. The method for manufacturing the novel diaphragm according to claim 10, characterized in that, The manufacturing method further includes: Drying step: The novel diaphragm is dried to form a dried novel diaphragm.

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