Temperature-resistant and puncture-resistant separator for energy storage battery and preparation method thereof

Abstract

This invention provides a temperature- and puncture-resistant separator for energy storage batteries and its preparation method. The separator comprises an aramid-based film and a safety coating disposed on at least one surface of the aramid-based film. The safety coating comprises nanodiamond, isoflurane diisocyanate adhesive, and a composite flame-retardant material. The composite flame-retardant material comprises core-shell structured particles, each particle comprising: a core comprising organic polymer nanospheres formed from a copolymer of phosphorus-containing and nitrogen-containing monomers; and a shell primarily formed of a polymethyl methacrylate matrix, wherein the shell incorporates thermosensitive cracking monomers and low glass transition temperature monomers. This invention combines the excellent mechanical strength and thermal stability of the aramid-based film with the rapid thermal response and efficient flame-retardant properties of the composite flame-retardant material, forming multiple safety guarantees of physical isolation and chemical flame retardancy, significantly improving the safety performance of lithium-ion batteries under high temperature and mechanical abuse conditions.

Description

Technical Field

[0001] This invention relates to the field of new energy storage battery technology, specifically to a temperature- and puncture-resistant separator for energy storage batteries and its preparation method. Background Technology

[0002] With the rapid development of new energy technologies, lithium-ion batteries have been widely used in energy storage systems due to their advantages such as high energy density and long cycle life. However, lithium-ion batteries may experience thermal runaway under abnormal conditions such as overcharging, short circuits, punctures, and compression, leading to fires or even explosions, which seriously affects their application in fields with high safety requirements.

[0003] As a key component of lithium-ion batteries, the separator not only needs to possess excellent ion conductivity but also sufficient safety assurance capabilities under abnormal conditions. Traditional polyolefin separators (such as polyethylene and polypropylene), while exhibiting good chemical stability and ion conductivity, are prone to shrinkage or even melting at high temperatures, leading to short circuits at the positive and negative electrodes and triggering thermal runaway. Furthermore, these separators are easily punctured under mechanical abuse conditions such as needle penetration, failing to prevent the occurrence and propagation of internal short circuits.

[0004] To improve the safety performance of separators, the industry has developed various improvement solutions. For example, battery safety can be improved by coating the electrode material surface with a safety coating containing polyethylene microspheres. However, when the temperature reaches the melting temperature of the polyethylene microspheres, they begin to melt and flow into a thin film. But because the melting temperature range is narrow (about 120°C), when the temperature exceeds this range by a significant amount, this protective film will crack, resulting in a decrease in flame retardant effect.

[0005] Furthermore, patent application number 201910386330.1 discloses a membrane coating for core-shell structured flame-retardant particles. However, due to the time lag between the melting of the outer shell and the release of the flame retardant, the reaction rate is slower than the thermal runaway process, making it difficult to exert the flame-retardant effect in a timely manner. In addition, the preparation of this solution requires complex processes such as ball milling and spray granulation, which are complex, energy-intensive, and not conducive to large-scale production.

[0006] On the other hand, aramid materials, with their excellent mechanical strength and thermal stability, are gradually being used in the field of lithium-ion battery separators. However, although pure aramid separators have good heat resistance and mechanical strength, they lack active safety functions under thermal runaway conditions, cannot form a thermal barrier to block ion transport at high temperatures, and do not have flame retardant capabilities.

[0007] Therefore, there is an urgent need to develop a lithium-ion battery separator that combines the excellent heat resistance and mechanical strength of aramid materials with active thermal response and flame retardant functions to comprehensively improve the safety performance of lithium-ion energy storage batteries. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing lithium-ion energy storage battery separators in terms of temperature resistance, puncture resistance, and flame retardancy by providing a temperature- and puncture-resistant separator for energy storage batteries and its preparation method. This separator combines the excellent mechanical properties and thermal stability of aramid-based films with the rapid thermal response and efficient flame retardant characteristics of composite flame-retardant materials, providing multiple safety guarantees under high temperature and mechanical abuse conditions.

[0009] To achieve the above objectives, the present invention provides the following technical solution:

[0010] In a first aspect, the present invention provides a heat- and puncture-resistant separator for energy storage batteries, comprising:

[0011] Aramid-based films; and

[0012] A safety coating disposed on at least one surface of the aramid-based film, the safety coating comprising nanodiamond, isoflurone diisocyanate adhesive and composite flame retardant material;

[0013] The composite flame-retardant material comprises core-shell structured particles, wherein the particles include:

[0014] The core comprises organic polymer nanospheres formed from copolymers of phosphorus-containing and nitrogen-containing monomers, with a particle size of 50-200 nm; and

[0015] The shell is mainly formed of polymethyl methacrylate matrix, and the shell is doped with thermosensitive cracking monomers and low glass transition temperature monomers, with a thickness of 5-20 nm.

[0016] Optionally, the phosphorus-containing monomer is selected from at least one of phosphate methacrylate, di[2-(acryloyloxy)ethyl] phosphate, and dimethyl allyl phosphate.

[0017] Optionally, the nitrogen-containing monomer is selected from at least one of acrylamide and N-vinylpyrrolidone.

[0018] Optionally, the core further includes a fluorinated monomer selected from at least one of 2,2,2-trifluoroethyl acrylate, perfluorobutyl ethyl methacrylate, and perfluorohexyl ethyl methacrylate.

[0019] Optionally, the thermosensitive cracking monomer is selected from at least one of di-tert-butyl acrylate peroxide, tert-butyl peroxide isopropyl carbonate, 2,2'-azo[2-methyl-N-(2-hydroxyethyl)propionamide], and 1,1'-azo(cyclohexane-1-benzonitrile).

[0020] Optionally, the low glass transition temperature monomer is selected from at least one of butyl acrylate and isooctyl acrylate.

[0021] Optionally, the content of the shell layer is 20-90 wt%, based on the total weight of the composite flame retardant material.

[0022] Optionally, the content of the thermosensitive cracking monomer in the shell is 1-10 wt%, and the content of the low glass transition temperature monomer in the shell is 5-30 wt%.

[0023] Optionally, the average particle size of the nanodiamond is 50-500 nm.

[0024] Optionally, in the safety coating, the content of the nanodiamond is 60-85 wt%, the content of the isoflurane diisocyanate adhesive is 5-20 wt%, and the content of the composite flame retardant material is 10-20 wt%, based on the total weight of the safety coating.

[0025] Optionally, the thickness of the aramid-based film is 5-30 μm.

[0026] Optionally, the thickness of the safety coating is 1-10 μm.

[0027] Optionally, the safety coating is disposed on both surfaces of the aramid-based film.

[0028] Optionally, the isoflurane diisocyanate adhesive protrudes from the surface of the safety coating, and the average particle size d1 of the isoflurane diisocyanate adhesive is larger than the average particle size d2 of the composite flame retardant material and the average particle size d3 of the nanodiamond; and they satisfy the following relationships: d1 / d2=(3~8):1, d1 / d3=(3~8):1. The isoflurane diisocyanate adhesive protruding from the surface of the safety coating is achieved by controlling the sizes of the isoflurane diisocyanate adhesive, the composite flame retardant material, and the nanodiamond. This protruding isoflurane diisocyanate adhesive can bond with adjacent positive and negative electrode sheets in the lithium-ion battery, thereby suppressing battery deformation and further ensuring battery safety and flatness.

[0029] Optionally, the surface of the aramid-based film is subjected to corona treatment to form a rough surface, wherein the voltage of the corona treatment is 2.0~2.2kV, the current is 8A, the corona velocity is 40~50m / min, and the treatment time is 8~10s.

[0030] Secondly, the present invention provides a method for preparing the above-mentioned temperature-resistant and puncture-resistant separator for energy storage batteries, comprising the following steps:

[0031] (1) Preparation of the composite flame-retardant material:

[0032] (1a) Disperse phosphorus-containing monomers and nitrogen-containing monomers in deionized water and emulsifier, add initiator, and carry out emulsion polymerization at 50-80℃ to obtain kernel seed emulsion;

[0033] (1b) Methyl methacrylate, thermosensitive cracking monomer, low glass transition temperature monomer and initiator are added to the kernel seed emulsion, and secondary emulsion polymerization is carried out at 50-70°C to form a shell layer;

[0034] (1c) Cool, wash, centrifuge and dry the product to obtain the composite flame retardant material;

[0035] (2) Preparation of safety coating slurry:

[0036] The composite flame retardant material, the nanodiamond and the isoflurone diisocyanate adhesive are dispersed in a solvent and stirred evenly to obtain a safety coating slurry.

[0037] (3) Apply a safety coating:

[0038] The safety coating slurry is applied to at least one surface of the aramid-based membrane, and after drying, the heat-resistant and puncture-resistant separator for energy storage batteries is obtained.

[0039] Optionally, a fluorinated monomer is also added in step (1a), wherein the fluorinated monomer is selected from at least one of 2,2,2-trifluoroethyl acrylate, perfluorobutyl ethyl methacrylate, and perfluorohexyl ethyl methacrylate.

[0040] Optionally, in step (1a), the emulsifier is selected from at least one of sodium dodecyl sulfate (SDS), nonylphenol polyoxyethylene ether (OP-10), and sodium dodecylbenzene sulfonate; and the initiator is selected from at least one of ammonium persulfate, potassium persulfate, and azobisisobutyronitrile.

[0041] Optionally, in step (1b), the mixture of methyl methacrylate, thermosensitive cracking monomer and low glass transition temperature monomer is added dropwise in 3-5 batches over 1-2 hours, and an initiator solution is added simultaneously during the dropwise addition to control the shell thickness.

[0042] Optionally, in step (2), the solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, cyclohexanone, and ethanol.

[0043] Optionally, the solid content in the safety coating slurry is 10-40 wt%.

[0044] Optionally, in step (3), at least one of the following methods is used to coat the safety coating slurry onto the surface of the aramid base film: scraping, dipping, or spraying.

[0045] Optionally, the drying temperature is 60-80℃ and the drying time is 1-5 hours.

[0046] Thirdly, the present invention provides a lithium-ion energy storage battery comprising the above-mentioned temperature-resistant and puncture-resistant separator for energy storage batteries.

[0047] Compared with the prior art, the present invention has at least the following beneficial effects:

[0048] 1) Multiple Safety Mechanisms: The lithium-ion battery separator of this invention combines the excellent mechanical strength and thermal stability of the aramid-based film with the rapid thermal response and efficient flame-retardant properties of the composite flame-retardant material, forming multiple safety guarantees of physical isolation and chemical flame retardancy. The aramid-based film has a thermal decomposition temperature as high as 400℃ and excellent mechanical strength, enabling it to maintain physical isolation under high temperature and needle-puncture conditions; the nanodiamond in the safety coating enhances the separator's heat resistance, thermal conductivity, and puncture resistance; the composite flame-retardant material forms a heat-blocking film and releases flame-retardant components when the temperature rises, effectively suppressing thermal runaway. This multiple protection mechanism significantly improves the safety performance of lithium-ion batteries under extreme conditions.

[0049] 2) Rapid Thermal Response and Stepped Flame Retardancy: The composite flame-retardant material in the diaphragm of this invention has a unique core-shell structure. When the temperature rises to approximately 120°C, the shell layer first softens and forms a heat-blocking film, impeding lithium-ion transport. Simultaneously, the thermosensitive cracking monomer decomposes to generate gas, accelerating the release of flame-retardant components from the core. At higher temperatures (>150°C), the phosphorus-nitrogen or phosphorus-nitrogen-fluorine synergistic flame-retardant system in the core fully exerts its function, forming a dense carbonized layer and releasing flame-retardant gas. This stepped flame-retardant mechanism enables the diaphragm of this invention to continuously provide safety protection over a wide temperature range, effectively responding to different degrees of thermal runaway.

[0050] 3) Excellent mechanical strength and puncture resistance: The aramid-based membrane itself possesses excellent mechanical strength, which, combined with the heat-resistant coating on the surface, further enhances the puncture resistance of the separator. Tests show that the separator of this invention can effectively prevent the occurrence and propagation of internal short circuits in needle penetration tests. Even near the needle penetration point, the separator can still maintain basic physical isolation function, significantly reducing the safety risks of the battery under mechanical abuse conditions.

[0051] 4) Excellent electrochemical compatibility: The safety coating design of this invention takes into account compatibility with the electrolyte. The composite flame-retardant material uses polymethyl methacrylate as the shell matrix, which has excellent chemical stability and can effectively isolate the flame retardant in the core from direct contact with the electrolyte, avoiding the adverse effects of the flame retardant on the normal electrochemical performance of the battery. At the same time, the introduction of nanodiamonds provides better thermal conductivity, effectively improving the thermal conductivity of the safety coating. Cycle tests show that lithium-ion batteries using the separator of this invention have cycle performance and rate performance comparable to commercial separators.

[0052] 5) Simplified preparation process: The present invention uses a continuous two-step emulsion polymerization method to prepare core-shell structured composite flame retardant materials, which eliminates the need for complex steps such as ball milling and spray granulation. The process is simple, energy consumption is low, and it is suitable for large-scale production. In addition, the membrane is prepared using a conventional coating process, which is easy to be compatible with existing production lines and has good industrialization prospects. Attached Figure Description

[0053] Figure 1 This is a schematic diagram of the diaphragm structure in one embodiment of the present invention;

[0054] Figure 2 This is a schematic diagram of the diaphragm structure in another embodiment of the present invention.

[0055] In the diagram: 1. Aramid base film; 2. Safety coating. Detailed Implementation

[0056] 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, and 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.

[0057] like Figures 1-2 As shown, this invention provides a temperature- and puncture-resistant separator for energy storage batteries, comprising an aramid-based membrane 1 and a safety coating 2 disposed on at least one surface of the aramid-based membrane 1. The safety coating 2 comprises nanodiamonds, isoflurane diisocyanate adhesive, and a composite flame-retardant material. The composite flame-retardant material has a core-shell structure, comprising a core and a shell. The core comprises organic polymer nanospheres formed from copolymers of phosphorus-containing and nitrogen-containing monomers, with a particle size of 50-200 nm. The shell is mainly formed from a polymethyl methacrylate matrix, incorporating thermosensitive cracking monomers and low glass transition temperature monomers, with a thickness of 5-20 nm.

[0058] The working mechanism of the diaphragm of the present invention includes the following three levels:

[0059] First level (physical isolation): Aramid-based films, with their excellent mechanical strength and thermal stability, can still maintain basic physical isolation function under high temperature and needle-punching conditions, preventing direct contact between positive and negative electrodes.

[0060] The second layer (thermal barrier): When the temperature rises to about 120°C, the composite flame-retardant material shell in the safety coating softens and forms a heat-blocking film, which blocks lithium-ion transport and reduces the internal current of the battery.

[0061] The third level (chemical flame retardancy): When the temperature rises further (>150℃), the PN or PNF synergistic flame retardant system in the core plays a full role, forming a dense carbonized layer and releasing flame retardant gas, effectively inhibiting the further development of thermal runaway.

[0062] I. Composition of the diaphragm

[0063] Aramid-based membranes are porous membranes made from aromatic polyamide fibers using wet or dry processes, exhibiting excellent mechanical strength, thermal stability, and chemical resistance. In this invention, the preferred thickness of the aramid-based membrane is 5-30 μm, the porosity is 30-70%, and the average pore size is 20-200 nm. The aramid-based membrane is commercially available.

[0064] The safety coating consists of three main components: nano-diamonds, isoflurane diisocyanate adhesive, and composite flame-retardant materials.

[0065] Nanodiamond particles possess high melting points, high hardness, and excellent thermal stability, enabling them to maintain structural stability at high temperatures and prevent membrane shrinkage. Furthermore, as the material with the highest known thermal conductivity in nature (approximately 2000~2200 W / (m·K)), nanodiamond acts as a highly efficient thermally conductive filler in coatings, constructing microscopic pathways for rapid heat conduction.

[0066] The average particle size of nanodiamonds is preferably 50-500 nm. If the particle size is too small, although a more uniform coating can be formed, it may lead to a decrease in porosity and affect ion conduction; if the particle size is too large, it may lead to an uneven coating structure and affect mechanical properties.

[0067] Isoflurane diisocyanate (IPDI) adhesive is used to bond nanodiamonds and composite flame-retardant materials to the surface of aramid-based films, forming a stable coating structure. Furthermore, the ends of the IPDI molecular chains are rich in highly reactive isocyanate groups (-NCO). These groups can chemically react with hydroxyl groups (-OH) and other active hydrogen-containing groups generated on the rough surface of the base film after corona treatment, forming strong urethane bonds. This chemical bonding significantly improves interlayer adhesion, preventing coating peeling caused by thermal expansion and contraction or vibration. Moreover, the IPDI adhesive itself has good weather resistance and hydrolysis resistance, ensuring the stability of the coating under long-term use conditions.

[0068] The composite flame-retardant material is the core component of this invention. It has a unique core-shell structure, can respond quickly at high temperatures, and provides dual functions of heat blocking and flame retardancy.

[0069] The core is formed by copolymerization of phosphorus-containing and nitrogen-containing monomers, and fluorine-containing monomers can be selectively introduced to form a PN or PNF synergistic flame retardant system.

[0070] Phosphorus-containing monomers primarily provide a condensed-phase flame-retardant effect, forming phosphoric acid and its derivatives at high temperatures, promoting carbonization to form a dense protective layer. In this invention, the phosphorus-containing monomers are preferably selected from at least one of phosphate methacrylate, di[2-(acryloyloxy)ethyl]phosphate, and dimethyl allyl phosphate. These monomers all contain polymerizable carbon-carbon double bonds, enabling them to participate in free radical polymerization reactions, and also contain phosphate groups, releasing phosphoric acid during thermal decomposition to promote material carbonization.

[0071] Nitrogen-containing monomers primarily provide a gas-phase flame-retardant effect, releasing non-combustible gases such as nitrogen at high temperatures, diluting the concentration of combustible gases, and inhibiting combustion. In this invention, the nitrogen-containing monomer is preferably selected from at least one of acrylamide and N-vinylpyrrolidone. These monomers contain nitrogen atoms, decompose at high temperatures to release nitrogen gas, and can synergistically work with phosphorus-containing monomers to enhance the carbonization effect.

[0072] Fluorinated monomers primarily provide gas-phase flame retardancy and cooling effects, releasing fluorinated gas at high temperatures to capture free radicals and block combustion chain reactions. In this invention, the fluorinated monomers are preferably selected from at least one of 2,2,2-trifluoroethyl acrylate, perfluorobutyl ethyl methacrylate, and perfluorohexyl ethyl methacrylate. These monomers contain fluorine atoms and release fluorinated gas upon thermal decomposition, forming a triple synergistic flame retardant effect with the PN system.

[0073] The shell is mainly formed by polymethyl methacrylate (PMMA) matrix, while introducing thermosensitive cracking monomers and low glass transition temperature monomers to achieve rapid thermal response and good film-forming properties.

[0074] PMMA matrix exhibits excellent chemical stability and film-forming properties, effectively isolating the core from the external environment and preventing direct contact between flame retardants and electrolytes. Simultaneously, PMMA begins to soften at approximately 120°C, forming a heat-blocking film that impedes lithium-ion transport and reduces internal battery current.

[0075] Thermosensitive cracking monomers decompose under heating conditions to generate gas, forming microporous channels in the shell and accelerating the release of the core flame retardant. In this invention, the thermosensitive cracking monomer is preferably selected from at least one of di-tert-butyl acrylate peroxide, tert-butyl peroxide isopropyl carbonate, 2,2'-azo[2-methyl-N-(2-hydroxyethyl)propionamide], and 1,1'-azo(cyclohexane-1-benzonitrile). These monomers contain heat-sensitive groups and decompose to generate gas in the range of 120-150°C, forming a microporous structure.

[0076] Low glass transition temperature monomers are mainly used to adjust the glass transition temperature of the shell layer, enhancing its flexibility and adhesion. In this invention, the low glass transition temperature monomer is preferably selected from at least one of butyl acrylate and isooctyl acrylate. These monomers have low Tg homopolymers (butyl acrylate Tg is approximately -54°C, isooctyl acrylate Tg is approximately -50°C), which can reduce the overall Tg of the shell layer, causing the shell layer to soften at lower temperatures and improving the thermal response rate.

[0077] Specifically, based on the total weight of the composite flame-retardant materials, the shell content is preferably 20-90 wt%, more preferably 40-80 wt%. If the shell content is too low, it cannot effectively isolate the core from the electrolyte, affecting the normal performance of the battery; if the shell content is too high, the core flame retardant content is insufficient, reducing the flame-retardant effect.

[0078] In the shell composition, based on the total mass of the shell monomers, the preferred mass percentage of methyl methacrylate is 60-94%, the preferred mass percentage of thermosensitive cracking monomers is 1-10%, and the preferred mass percentage of low glass transition temperature monomers is 5-30%. If the content of thermosensitive cracking monomers is too low, micropore formation is insufficient, and flame retardant release is slow; if the content is too high, shell strength decreases. If the content of low glass transition temperature monomers is too low, shell flexibility is insufficient; if the content is too high, shell strength decreases.

[0079] In the core composition, the total mass of the core monomers is used as the measurement standard. The mass percentage of phosphorus-containing monomers is preferably 40-80%, and the mass percentage of nitrogen-containing monomers is preferably 20-60%. When fluorine-containing monomers are added, the mass percentage of fluorine-containing monomers is preferably 5-30%. At this time, the amount of phosphorus-containing monomers and nitrogen-containing monomers is adjusted proportionally.

[0080] Among them, based on the total weight of the safety coating, the content of nanodiamond is preferably 60-85wt%, the content of isoflurane diisocyanate adhesive is preferably 5-20wt%, and the content of composite flame retardant material is preferably 10-20wt%.

[0081] If the nanodiamond content is too low, it cannot provide sufficient thermal stability and mechanical strength; if the content is too high, it may lead to decreased coating adhesion and easy peeling. If the isoflurane diisocyanate adhesive content is too low, the coating structure will be unstable; if the content is too high, it may clog pores and affect ion conduction. If the composite flame retardant material content is too low, the flame retardant effect will be insignificant; if the content is too high, it may affect the electrochemical performance of the diaphragm.

[0082] II. Preparation method of diaphragm

[0083] The method for preparing the temperature-resistant and puncture-resistant lithium-ion battery separator of the present invention includes three main steps: preparing composite flame-retardant materials, preparing safety coating slurry, and applying a safety coating.

[0084] 1. Preparation of composite flame-retardant materials

[0085] The composite flame-retardant material is prepared by a two-step emulsion polymerization method, the specific steps of which are as follows:

[0086] 1.1 Kernel Preparation

[0087] A phosphorus-containing monomer and a nitrogen-containing monomer (or a fluorine-containing monomer) are dispersed in deionized water and an emulsifier. An initiator is added, and emulsion polymerization is carried out at 50-80°C to obtain a kernel seed emulsion.

[0088] The emulsifier is selected from at least one of sodium dodecyl sulfate (SDS), nonylphenol polyoxyethylene ether (OP-10), and sodium dodecylbenzene sulfonate, or a combination thereof. The amount of emulsifier used is generally 0.5-3% of the mass of the aqueous phase.

[0089] The initiator is selected from at least one of ammonium persulfate (APS), potassium persulfate (KPS), and azobisisobutyronitrile (AIBN). The amount of initiator used is generally 0.5-2% of the total mass of the monomers.

[0090] 1.2 Shell Preparation

[0091] Methyl methacrylate, a thermosensitive cracking monomer, a low glass transition temperature monomer, and an initiator are added to the kernel seed emulsion, and a secondary emulsion polymerization is carried out at 50-70℃ to form a shell layer.

[0092] To control the uniformity of shell thickness, the shell monomer mixture is preferably added dropwise in 3-5 batches over 1-2 hours, along with the initiator solution. The polymerization time is 1-3 hours. Batch addition ensures uniform polymerization of the monomers on the core surface, preventing the formation of new monomer particles.

[0093] The dropping rate of the initiator solution is synchronized with the dropping rate of the monomer to ensure that the monomer can polymerize on the core surface in a timely manner to form a uniform shell.

[0094] 1.3 Post-processing

[0095] The polymerized product was cooled to room temperature, then washed, centrifuged, and dried to obtain a powdered core-shell structured composite flame retardant material.

[0096] Centrifugation conditions are generally 6000-10000 rpm for 10-30 minutes; drying conditions are vacuum drying at 40-60℃ for 12-24 hours.

[0097] 2. Preparation of safety coating slurry

[0098] The composite flame retardant material, nanodiamond and isoflurane diisocyanate adhesive are dispersed in a suitable solvent in a predetermined ratio and stirred evenly to obtain a safety coating slurry.

[0099] The solvent can be at least one of N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), and cyclohexanone.

[0100] The solid content of the safety coating slurry is preferably 10-40 wt%. If the solid content is too low, it is difficult to control the coating thickness and the efficiency is low; if the solid content is too high, the slurry viscosity is high, which is not conducive to uniform coating.

[0101] In the slurry preparation process, isoflurane diisocyanate adhesive is usually dissolved in a solvent first, and then nanodiamond and composite flame retardant materials are added. The mixture is then dispersed by ball milling, ultrasonication or high-speed shearing to finally obtain a uniform and stable slurry.

[0102] Preferably, the isophorone diisocyanate adhesive protrudes from the surface of the safety coating, and the average particle size d1 of the isophorone diisocyanate adhesive is larger than the average particle size d2 of the composite flame retardant material and the average particle size d3 of the nanodiamond; and they satisfy the following relationships: d1 / d2=(3~8):1, d1 / d3=(3~8):1. The isophorone diisocyanate adhesive protruding from the surface of the safety coating is achieved by controlling the sizes of the isophorone diisocyanate adhesive, the composite flame retardant material, and the nanodiamond. This protruding isophorone diisocyanate adhesive can bond with adjacent positive and negative electrode sheets in the lithium-ion battery, thereby suppressing battery deformation and further ensuring battery safety and flatness.

[0103] 3. Apply a safety coating

[0104] A safety coating slurry is applied to at least one surface of an aramid-based membrane, and after drying, a heat- and puncture-resistant separator for energy storage batteries is obtained.

[0105] Among them, conventional coating techniques such as scraping, dip coating, and spraying can be selected for the coating method.

[0106] After coating, dry at 60-80℃ for 1-5 hours to ensure complete solvent evaporation and the formation of a stable coating structure. Too low a drying temperature will result in residual solvent affecting performance; too high a temperature may cause premature activation of the composite flame retardant material or degradation of the isoflurane diisocyanate adhesive.

[0107] For membranes requiring double-sided coating, a two-step single-sided coating process or a single dip-coating process can be used. Double-sided coating provides more comprehensive safety protection, but it also increases membrane thickness and affects energy density.

[0108] Preferably, such as Figures 1-2As shown, the surface of the aramid-based film is roughened by corona treatment. The corona treatment voltage is 2.0~2.2kV, the current is 8A, the corona velocity is 40~50m / min, and the treatment time is 8~10s.

[0109] The inventors discovered through testing the adhesion of the safety coating that the aramid-based film treated with corona discharge exhibited significantly improved adhesion and strength. The coating strength was highest when the corona current reached 8A; however, adhesion decreased sharply when the current exceeded 8A. This demonstrates that the magnitude of the corona current plays a decisive role in the adhesion of the aramid-based film. As the corona current increases, the kinetic energy of the discharged particles increases, which is beneficial for opening the chemical bonds of the long molecular chains on the film surface. This gradually increases the surface activity energy and surface tension, thus aiding in the adhesion and bonding of the adhesive. Further research revealed that the peak surface tension of the aramid-based film occurred at a corona current of approximately 8A; as the current continued to increase, the surface tension decreased. This is because the air volume between the electrode and the corona roller has reached a relatively stable state, and the oxygen molecule content in the air is constant. Even increasing the voltage and current cannot activate more oxygen molecules, thus preventing more oxygen-containing functional groups from remaining on the film surface. Simultaneously, excessive corona discharge severely damages the surface structure of the film, leading to a rapid decrease in surface tension.

[0110] Compared to untreated aramid-based films, corona treatment significantly improved the adhesion of the safety coating on the film surface. Surface tension increased substantially with increasing corona current, reaching its maximum at 8A. Furthermore, excessively fast corona treatment speed or insufficient treatment time resulted in inadequate treatment and decreased adhesion; conversely, excessively slow treatment speed or excessively long treatment time easily led to corona breakdown, causing adhesive re-adhesion. Therefore, it is crucial to control the corona treatment speed and time within a suitable range.

[0111] Further comparison revealed that the maximum depth of the aramid film surface without corona treatment was no more than 28 nm, while the maximum depth after corona treatment reached 70 nm. The surface exhibited obvious unevenness, with the raised areas being brighter in color. Analysis showed that these brighter areas were granular materials, mainly composed of low molecular weight oxides. The changes in surface roughness and the increase in the actual micro-area accurately reflect the impact of corona treatment on the structure and composition of the aramid film. Specific Implementation

[0112] The following examples are used to further illustrate the present invention, but do not constitute a limitation on the scope of protection of the present invention.

[0113] Example 1

[0114] 1. Preparation of composite flame-retardant materials:

[0115] raw material:

[0116] Phosphorus-containing monomer: 20g of di[2-(acryloyloxy)ethyl] phosphate;

[0117] Nitrogen-containing monomer: Acrylamide (AM) 10g;

[0118] Deionized water: 200g;

[0119] Emulsifiers: Sodium dodecyl sulfate (SDS) 1g, nonylphenol polyoxyethylene ether (OP-10) 1g;

[0120] Initiator: Ammonium persulfate (APS) 0.5g;

[0121] Shell monomers: methyl methacrylate (MMA) 5g, di-tert-butyl peroxide 0.2g, butyl acrylate (BA) 0.8g;

[0122] Shell initiator: Potassium persulfate (KPS) 0.2g.

[0123] Preparation method:

[0124] (1) Add deionized water, SDS and OP-10 to a four-necked flask and stir until dissolved;

[0125] (2) Add di[2-(acryloyloxy)ethyl] phosphate and AM mixed monomer solution, and stir at room temperature for 20 minutes to form a pre-emulsion;

[0126] (3) Purge nitrogen gas for 10 minutes, raise the temperature to 60°C, add APS solution (dissolved in 10g water), and react for 4 hours to obtain kernel seed emulsion;

[0127] (4) Cool down to 50°C and prepare a mixture of MMA, di-tert-butyl acrylate peroxide and BA. Add the mixture in three batches over one hour (20% of the total amount in the first batch, 30% of the total amount in the second batch, and 50% of the total amount in the third batch). At the same time, add KPS solution (dissolved in 10g of water).

[0128] (5) After reacting at 50°C for 2 hours, cool to room temperature;

[0129] (6) The product was centrifuged (8000 rpm, 15 minutes), washed three times with deionized water, centrifuged again, and finally vacuum dried at 50°C for 18 hours to obtain a powdered core-shell structure (PN core / PMMA shell) composite flame retardant material.

[0130] Composite flame retardant material product characteristics: average particle size is 120nm; shell thickness is about 10nm; shell content is about 25wt%.

[0131] 2. Preparation of the diaphragm:

[0132] raw material:

[0133] Aramid-based film: 15μm thickness, 45% porosity;

[0134] Nanodiamond: average particle size 100nm, 10g;

[0135] Isoflurone diisocyanate adhesive: 1.5g;

[0136] Composite flame retardant material: 2g;

[0137] Solvent: NMP, 86.5g.

[0138] Preparation method:

[0139] (1) Dissolve isoflurane diisocyanate in NMP and stir until completely dissolved;

[0140] (2) Add nanodiamond and composite flame retardant material, ball mill for 12 hours to obtain a uniform slurry with a solid content of about 13.5%;

[0141] (3) Use an automatic coating machine and a doctor blade method to coat the slurry onto one side of the aramid base film to control the wet film thickness;

[0142] (4) Dry in an oven at 80℃ for 2 hours to obtain a single-sided coated diaphragm;

[0143] (5) Repeat steps (3) and (4) to coat the other side of the base film to obtain a double-coated diaphragm.

[0144] Diaphragm product characteristics:

[0145] Total thickness: approximately 25 μm (base film 15 μm, coating on each side approximately 5 μm);

[0146] Porosity: Approximately 40%;

[0147] Coating composition: 74.1 wt% nano-diamond, 11.1 wt% isoflurane diisocyanate, and 14.8 wt% composite flame retardant material.

[0148] Example 2

[0149] 1. Preparation of composite flame-retardant materials:

[0150] raw material:

[0151] Phosphorus-containing monomer: 15g of di[2-(acryloyloxy)ethyl] phosphate;

[0152] Nitrogen-containing monomer: Acrylamide (AM) 8g;

[0153] Fluorinated monomer: 2,2,2-trifluoroethyl acrylate (TFEMA) 7g;

[0154] Deionized water: 200g;

[0155] Emulsifier: SDS / OP-10 = 1:1, total amount 2g;

[0156] Initiator: APS 0.5g;

[0157] Shell monomers: MMA 5g, di-tert-butyl acrylate peroxide 0.5g, BA 1g;

[0158] Shell initiator: KPS 0.3g.

[0159] Preparation method:

[0160] Following the steps in Example 1, a core seed emulsion containing PNF monomers was prepared, followed by shell polymerization to finally obtain a core-shell structure (PNF core / PMMA shell) composite flame retardant material.

[0161] Composite flame retardant material product characteristics: average particle size is 130nm; shell thickness is about 12nm; shell content is about 30wt%.

[0162] 2. Preparation of the diaphragm:

[0163] raw material:

[0164] Aramid-based film: 20μm thickness, 50% porosity;

[0165] Nanodiamonds: average particle size 80nm, 10g;

[0166] Isoflurone diisocyanate adhesive: 2g;

[0167] Composite flame retardant material: 3g;

[0168] Solvent: NMP, 85g.

[0169] Preparation method:

[0170] (1) Dissolve isoflurane diisocyanate in NMP and stir until completely dissolved;

[0171] (2) Add nanodiamond and composite flame retardant material, ball mill for 15 hours to obtain a uniform slurry with a solid content of about 15%;

[0172] (3) Use dip coating method to immerse the aramid-based film in the slurry, and control the soaking time and lifting speed;

[0173] (4) Dry in an oven at 70°C for 3 hours to obtain a double-coated diaphragm.

[0174] Diaphragm product characteristics:

[0175] Total thickness: approximately 32 μm (base film 20 μm, coatings on both sides total approximately 12 μm);

[0176] Porosity: Approximately 38%;

[0177] Coating composition: 66.7wt% nanodiamond, 13.3wt% isoflurane diisocyanate, and 20wt% composite flame retardant material.

[0178] Example 3

[0179] The preparation of the composite flame-retardant material is the same as in Example 1, except for the preparation of the diaphragm:

[0180] raw material:

[0181] Aramid-based film: 10 μm thickness, 55% porosity;

[0182] Nanodiamonds: average particle size 50nm, 8g;

[0183] Isoflurone diisocyanate adhesive: 1g;

[0184] Composite flame retardant material: 1.5g of the composite flame retardant material prepared in Example 1;

[0185] Solvent: NMP, 89.5g.

[0186] Preparation method:

[0187] (1) Dissolve isoflurane diisocyanate in NMP and stir until completely dissolved;

[0188] (2) After adding nanodiamond and composite flame retardant material, ultrasonically disperse for 2 hours, and then high-speed shear dispersion for 1 hour, a uniform slurry with a solid content of about 10.5% was obtained.

[0189] (3) Use a spraying method to evenly spray the slurry onto both sides of the aramid base film;

[0190] (4) Dry in an oven at 60°C for 4 hours to obtain a double-coated diaphragm.

[0191] Diaphragm product characteristics:

[0192] Total thickness: approximately 16 μm (base film 10 μm, coatings on both sides total approximately 6 μm);

[0193] Porosity: Approximately 42%;

[0194] Coating composition: 76.2 wt% nano-diamond, 9.5 wt% isoflurane diisocyanate adhesive, and 14.3 wt% composite flame retardant material.

[0195] Example 4

[0196] Unlike Example 2, the preparation method of the diaphragm in this example is as follows: before coating with the safety coating slurry, the aramid-based membrane is subjected to corona treatment, wherein the voltage of the corona treatment is 2.1kV, the current is 8A, the corona velocity is 45m / min, and the treatment time is 9s; and the corona-treated aramid-based membrane is then cleaned and dried before coating with the safety coating slurry. Other aspects are the same as in Example 2, and will not be repeated here.

[0197] Comparative Example 1: Ceramic-coated aramid membrane without composite flame-retardant materials

[0198] raw material:

[0199] Aramid-based film: 15μm thickness, 45% porosity;

[0200] Alumina ceramic particles: average particle size 100nm, 10g;

[0201] Isoflurone diisocyanate adhesive: 2g;

[0202] Solvent: NMP, 88g.

[0203] Preparation method:

[0204] Following the method of Example 1, but without adding composite flame retardant materials, a coated membrane containing only alumina ceramic particles was prepared.

[0205] Comparative Example 2: Commercial Polyolefin Separator

[0206] Commercially available polypropylene / polyethylene (PP / PE) composite membranes are used, with a thickness of 25μm, a porosity of 40%, and no coating.

[0207] IV. Performance Testing and Result Analysis

[0208] 1. Material Characterization

[0209] (1) Morphology analysis: Field emission scanning electron microscopy (FE-SEM) was used to observe the surface and cross-sectional morphology of the diaphragm and to evaluate the coating uniformity and adhesion.

[0210] (2) Porosity determination: The porosity of the membrane was determined by the butorol method.

[0211] (3) Ionic conductivity test: The ionic conductivity of the membrane was determined by AC impedance method in 1M LiPF6 EC / DMC (1:1 volume ratio) electrolyte.

[0212] (4) Heat shrinkage test: Place the diaphragm sample (5cm×5cm) in an oven preheated to a specific temperature (150℃) and keep it for 30 minutes. Measure the dimensional changes before and after heat treatment and calculate the heat shrinkage rate.

[0213] 2. Mechanical performance testing

[0214] (1) Tensile strength test: The tensile strength and elongation at break of the diaphragm were determined using a universal testing machine in accordance with ASTM D882 standard.

[0215] (2) Puncture strength test: Using a puncture tester, the force required for the diaphragm to be punctured by a Φ1mm steel needle is determined.

[0216] 3. Safety performance testing

[0217] (1) Thermal shutdown test: Electrodes are assembled on both sides of the diaphragm, immersed in electrolyte, and the temperature is gradually increased. The resistance change at different temperatures is measured to determine the thermal shutdown temperature and the resistance increase factor.

[0218] (2) Needle penetration flame retardant test: Perform a standard needle penetration test (Φ2mm steel needle) on a fully charged button cell, and record the battery temperature change and whether it catches fire or explodes.

[0219] (3) Thermal abuse test: Place the fully charged battery in an oven and heat it from room temperature to 200°C at a rate of 5°C / min. Record the change in battery surface temperature and whether it catches fire or explodes.

[0220] 4. Electrochemical performance testing

[0221] (1) Cyclic performance test: At 25℃, 100 cycles were performed with a charge and discharge current of 0.5C, and the capacity retention rate was recorded.

[0222] (2) Rate performance test: At 25℃, discharge tests were conducted at currents of 0.2C, 0.5C, 1C, 2C and 5C respectively, and the discharge capacity at each rate was recorded.

[0223] 5. Test Results and Analysis

[0224] Table 1 Comparison of basic diaphragm performance

[0225]

[0226] As shown in Table 1, the temperature-resistant and puncture-resistant diaphragm of the present invention exhibits excellent overall performance. Compared with commercial PP / PE diaphragms (Comparative Example 2), the thermal shrinkage rate of the diaphragm of the present invention is significantly reduced, from 58.5% to 1.3-3.0%, indicating excellent thermal stability. Simultaneously, both tensile strength and puncture strength are significantly improved, demonstrating superior mechanical properties.

[0227] Compared to the ceramic-coated aramid separator without composite flame retardant material (Comparative Example 1), the separator with added composite flame retardant material showed a slight decrease in ionic conductivity and porosity, but the difference was not significant and still met the requirements for normal battery operation. However, Example 4 exhibited superior performance in terms of thermal shrinkage and mechanical strength, thanks to the synergistic effect of aramid-based film corona treatment, composite flame retardant material, and nanodiamond.

[0228] Table 2. Test results of diaphragm safety performance

[0229]

[0230] Safety performance test results show that the diaphragm of the present invention has excellent thermal shutdown function and flame retardant properties. The diaphragms of Examples 1-4 begin thermal shutdown at approximately 120-125°C, with the resistance increasing rapidly by more than 100 times, effectively cutting off the current and preventing further development of thermal runaway. In contrast, the ceramic-coated aramid diaphragm without composite flame retardant material (Comparative Example 1) does not have a significant thermal shutdown function, and the resistance increase is less than 10 times; although the commercial PP / PE diaphragm has a thermal shutdown function, the temperature is high (135°C), and the resistance increase is small, resulting in insufficient safety margin.

[0231] The needle penetration test and thermal abuse test further demonstrated the excellent safety performance of the separator of the present invention. The battery using the separator of the present invention did not experience any fire or explosion in either the needle penetration or thermal abuse tests, exhibiting excellent safety performance. In contrast, Comparative Example 1 only experienced a short-term fire in the needle penetration test, but still caught fire in the thermal abuse test, indicating insufficient safety performance; Comparative Example 2 exhibited severe fire and explosion in both tests, demonstrating poor safety performance.

[0232] Table 3 Battery Cycle Performance Test Results

[0233]

[0234] Battery cycle performance test results show that the batteries using the separator of the present invention (Examples 1-4) have little difference in initial discharge capacity and cycle stability compared with the control group (Comparative Examples 1-2). This indicates that the separator of the present invention provides excellent safety performance without significantly affecting the electrochemical performance of the battery. This is due to the effective isolation of the core flame retardant by the core-shell composite flame retardant material, avoiding side reactions caused by direct contact between the flame retardant and the electrolyte.

[0235] In terms of high-rate discharge performance, Example 3 performed best, with a 5C discharge capacity retention of 84.6%, approaching the level of commercial membranes. This is mainly due to its thinner thickness (16 μm) and higher porosity (42%), which provides a shorter ion transport path and lower transport impedance. Examples 2 and 4, due to their larger thickness (32 μm), showed a slight decrease in high-rate performance, but still remained at an acceptable level.

[0236] Table 4 Temperature changes during needle prick test

[0237]

[0238] The temperature change data during the needle penetration test further demonstrates the excellent safety performance of the separator of the present invention. When the battery was punctured, the highest temperature in Examples 1-4 was controlled below 100°C, and the temperature rise did not exceed 70°C, which is far below the critical temperature for thermal runaway of lithium-ion batteries (approximately 150°C). This indicates that the separator of the present invention can effectively suppress internal short circuits and thermal runaway caused by needle penetration.

[0239] In contrast, although Comparative Example 1 used an aramid-based film and a ceramic coating, it lacked the thermal blocking and flame-retardant functions of the composite flame-retardant material. After being punctured, the temperature rose to 145.8°C, approaching the thermal runaway threshold, and a short-term fire occurred. Comparative Example 2, on the other hand, completely lost control, with the temperature rapidly rising to over 300°C, resulting in a violent fire and explosion.

[0240] Table 5 Analysis of Thermal Abuse Test Results

[0241]

[0242] The thermal abuse test results show that the batteries using the separator of this invention (Examples 1-4) exhibit a significant temperature plateau (approximately 120-135°C) during the heating process. This corresponds to the process where the composite flame-retardant material shell softens to form a heat-blocking film and releases the core flame retardant. Subsequently, the rate of temperature rise decreases significantly, with the maximum temperature controlled below 200°C. There was no rapid temperature rise characteristic of thermal runaway, nor did any fire occur.

[0243] In contrast, Comparative Example 1 began to release heat at approximately 135°C. Although the aramid-based film and ceramic coating provided some thermal barrier properties, they lacked active thermal response and flame-retardant functions, and the temperature continued to rise to 265°C, eventually leading to ignition. Comparative Example 2, on the other hand, had no thermal protection capabilities whatsoever, and the temperature rapidly rose to over 300°C, resulting in a violent fire.

[0244] Table 6. Changes in diaphragm performance at different temperatures

[0245]

[0246] Table 6 compares the performance changes of different diaphragms at various temperature points. The diaphragms of the present invention (Examples 1-4) begin to form a heat-blocking film at 120°C, the core flame retardant is rapidly released at 150°C, and they can still maintain basic physical isolation function at 180°C and 200°C to prevent short circuits. This is due to the excellent thermal stability of the aramid-based film (decomposition temperature > 400°C) and the dual functions of heat blocking and flame retardancy of the composite flame retardant material.

[0247] In contrast, the ceramic-coated aramid diaphragm without composite flame retardant material (Comparative Example 1) remained stable at lower temperatures but lacked thermal shutdown function, exhibiting localized short circuits at 180°C and large-area short circuits at 200°C; the commercial PP / PE diaphragm (Comparative Example 2) had already severely shrunk and partially melted at 150°C and completely failed at 180°C.

[0248] Based on the above test results, it can be seen that the temperature-resistant and puncture-resistant separator for energy storage batteries and its preparation method provided by this invention have the following significant advantages:

[0249] 1) Multiple safety protection mechanisms: Aramid base film provides excellent mechanical strength and thermal stability, nanodiamond enhances the heat resistance and puncture resistance of the membrane, and composite flame retardant material provides dual functions of heat blocking and flame retardancy, forming multiple safety protections of physical isolation and chemical flame retardancy.

[0250] 2) Rapid thermal response and wide temperature range protection: The core-shell structure design of the composite flame retardant material enables the diaphragm to quickly form a heat-blocking film at about 120°C, release the core flame retardant at about 150°C, and maintain physical isolation function above 200°C, providing comprehensive protection over a wide temperature range (above 120-200°C).

[0251] 3) Excellent mechanical properties and puncture resistance: The aramid-based membrane combined with the safety coating gives the diaphragm significantly improved tensile strength and puncture resistance, effectively preventing the occurrence and spread of internal short circuits under mechanical abuse conditions such as needle punching.

[0252] 4) Excellent electrochemical compatibility: The core-shell structure of the composite flame-retardant material ensures effective isolation between the flame retardant and the electrolyte, avoiding adverse effects on the normal electrochemical performance of the battery. Battery cycle tests show that the electrochemical performance of the separator of this invention is comparable to that of commercial separators.

[0253] 5) Simplified preparation process: Core-shell structured composite flame-retardant materials are prepared by continuous two-step emulsion polymerization, eliminating the need for complex steps such as ball milling and spray granulation; the diaphragm is prepared using conventional coating processes, which are easily compatible with existing production lines and have good industrialization prospects.

[0254] In summary, the temperature-resistant and puncture-resistant lithium-ion battery separator of the present invention achieves a balance of excellent thermal stability, mechanical strength, and active safety functions through the organic combination of aramid-based film, nano-diamond coating, and core-shell structure composite flame-retardant material. It provides a novel solution for improving the safety of lithium-ion batteries and has broad application prospects.

[0255] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0256] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to the specific implementations described. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A puncture and temperature resistant separator for energy storage batteries, characterized by, include: Aramid-based film; as well as A safety coating disposed on at least one surface of the aramid-based film, the safety coating comprising nanodiamond, isoflurone diisocyanate adhesive and composite flame retardant material; The composite flame-retardant material comprises core-shell structured particles, wherein the particles include: The core comprises organic polymer nanospheres formed from copolymers of phosphorus-containing and nitrogen-containing monomers, with a particle size of 50-200 nm; and The shell is mainly formed of polymethyl methacrylate matrix, and the shell is doped with thermosensitive cracking monomers and low glass transition temperature monomers, with a thickness of 5-20 nm.

2. The puncture and heat resistant separator for energy storage batteries according to claim 1, characterized by, The phosphorus-containing monomer is selected from at least one of phosphate methacrylate, di[2-(acryloyloxy)ethyl] phosphate, and dimethyl allyl phosphate; and / or, The nitrogen-containing monomer is selected from at least one of acrylamide and N-vinylpyrrolidone.

3. The puncture and heat resistant separator for energy storage batteries of claim 1, wherein, The core also includes a fluorinated monomer selected from at least one of 2,2,2-trifluoroethyl acrylate, perfluorobutyl ethyl methacrylate, and perfluorohexyl ethyl methacrylate.

4. The puncture and heat resistant separator for energy storage batteries of claim 1, wherein, The thermosensitive cracking monomer is selected from at least one of di-tert-butyl acrylate peroxide, tert-butyl peroxide isopropyl carbonate, 2,2'-azo[2-methyl-N-(2-hydroxyethyl)propionamide], and 1,1'-azo(cyclohexane-1-benzonitrile); and / or, The low glass transition temperature monomer is selected from at least one of butyl acrylate and isooctyl acrylate.

5. The puncture and heat resistant separator for energy storage batteries of claim 1, wherein, Based on the total weight of the composite flame-retardant material, the content of the shell layer is 20-90 wt%; and / or, The content of the thermosensitive cracking monomer in the shell is 1-10 wt%, and the content of the low glass transition temperature monomer in the shell is 5-30 wt%.

6. The puncture and heat resistant separator for energy storage batteries of claim 1, wherein, The average particle size of the nanodiamond is 50-500 nm.

7. The puncture and heat resistant separator for energy storage batteries of claim 1, wherein, In the safety coating, the total weight of the safety coating is used as the measurement standard, the content of the nanodiamond is 60-85wt%, the content of the isoflurane diisocyanate adhesive is 5-20wt%, and the content of the composite flame retardant material is 10-20wt%.

8. The puncture and heat resistant separator for energy storage batteries of claim 1, wherein, The thickness of the aramid-based film is 5-30 μm; and / or, The thickness of the safety coating is 1-10 μm.

9. A method of producing the temperature-resistant and puncture-resistant separator for energy storage batteries according to any one of claims 1 to 8, characterized by, Includes the following steps: (1) Preparation of the composite flame-retardant material: (1a) Disperse phosphorus-containing monomers and nitrogen-containing monomers in deionized water and emulsifier, add initiator, and carry out emulsion polymerization at 50-80℃ to obtain kernel seed emulsion; (1b) Methyl methacrylate, thermosensitive cracking monomer, low glass transition temperature monomer and initiator are added to the kernel seed emulsion, and secondary emulsion polymerization is carried out at 50-70°C to form a shell layer; (1c) Cool, wash, centrifuge and dry the product to obtain the composite flame retardant material; (2) Preparation of safety coating slurry: The composite flame retardant material, the nanodiamond and the isoflurone diisocyanate adhesive are dispersed in a solvent and stirred evenly to obtain a safety coating slurry. (3) Apply a safety coating: The safety coating slurry is applied to at least one surface of the aramid-based membrane, and after drying, the heat-resistant and puncture-resistant separator for energy storage batteries is obtained.

10. The method of claim 9, wherein, Step (1a) further includes the addition of a fluorinated monomer selected from at least one of 2,2,2-trifluoroethyl acrylate, perfluorobutyl ethyl methacrylate, and perfluorohexyl ethyl methacrylate; and / or, In step (1a), the emulsifier is selected from at least one of sodium dodecyl sulfate, nonylphenol polyoxyethylene ether, and sodium dodecylbenzene sulfonate; the initiator is selected from at least one of ammonium persulfate, potassium persulfate, and azobisisobutyronitrile; and / or, In step (1b), the mixture of methyl methacrylate, thermosensitive cracking monomer, and low glass transition temperature monomer is added dropwise in batches during the polymerization process, and an initiator solution is added simultaneously to control the shell thickness; and / or, In step (2), the solvent is selected from at least one of N-methylpyrrolidone, N,N-dimethylformamide, cyclohexanone, and ethanol; and / or, The safety coating slurry has a solid content of 10-40 wt%; and / or, In step (3), the safety coating slurry is applied to the surface of the aramid base film using at least one of the following methods: scraping, dipping, and spraying; and / or, The drying temperature is 60-80℃, and the drying time is 1-5 hours.

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