Heat-resistant diaphragm as well as preparation method and application thereof

Abstract

The invention relates to the technical field of new energy materials, in particular to a heat-resistant diaphragm and a preparation method and application thereof. According to the preparation method, the base membrane is subjected to plasma treatment, and the silane coupling agent self-assembly layer and the zirconium-boron hybrid layer are constructed, so that under the condition that the thickness of the diaphragm is not obviously increased, pore channels are not blocked, and the mechanical property, the heat resistance, the wettability and the ionic conductivity of the diaphragm can be greatly improved. And through preparation of the self-repairing coating, cracks can be self-repaired, and the heat resistance and the mechanical performance are further improved.

Description

Technical Field

[0001] This application relates to the field of new energy materials technology, specifically to a heat-resistant diaphragm, its preparation method, and its application. Background Technology

[0002] In recent years, lithium-ion batteries have been widely used in electronic products, new energy vehicles, and electrochemical energy storage due to their superior performance, such as high energy density and long cycle life. However, battery separators, as a key component of lithium-ion batteries, still face some unresolved issues. While traditional polyolefin separators such as polyethylene and polypropylene possess good mechanical properties and chemical stability, their thermal stability is poor, making them prone to shrinkage and collapse at high temperatures, affecting battery safety and electrical performance.

[0003] To improve the thermal stability of polyolefin separators, researchers have explored various modification methods, with coatings using various inorganic particles and ceramic coatings being a common approach. However, this method often results in a dense coating forming on the separator surface, clogging the separator's pores and reducing conductivity and lithium-ion transference number. Furthermore, traditional ceramic coatings are relatively thick, making them prone to microcracks, which affect the separator's mechanical properties and lifespan. In addition, polyolefin separators also suffer from poor wettability, poor electrolyte affinity, and low electrolyte retention, which directly impact conductivity and lithium-ion transference number.

[0004] For example, existing patent literature discloses a method for constructing a nano-coating for a lithium-ion battery separator. The steps include plasma treatment of a polyethylene separator, followed by coating the surface of the lithium-ion battery membrane and the surface of its three-dimensional pores with an aqueous nano-coating. This method can modify the separator surface and pores without increasing the separator thickness, thereby increasing the rate of ion passage through the separator and improving the ionic conductivity and lithium-ion transference number. However, it cannot achieve a balance between heat resistance and mechanical properties.

[0005] Currently, there is an urgent market demand for a new type of heat-resistant membrane that can improve the thermal stability of the membrane while maintaining good mechanical properties, good wettability, and electrochemical performance. Therefore, developing a heat-resistant membrane that can simultaneously meet these requirements is of great significance. Summary of the Invention

[0006] This application provides a heat-resistant separator, its preparation method, and its application, to solve the problems in the prior art where separators cannot simultaneously achieve thermal stability, mechanical properties, and wettability, thus affecting the separator's conductivity or lithium-ion transference number.

[0007] In a first aspect, this application provides a heat-resistant membrane, including a base membrane and a functional coating disposed on at least one side surface and / or interior of the base membrane; The heat-resistant diaphragm has a longitudinal wetting value of ≥2 mm and a transverse wetting value of ≥2 mm.

[0008] In one optional embodiment, the functional coating is a silane self-assembled layer and a zirconium-boron hybrid layer disposed on at least one side surface and / or inside the base film; the contact angle between the heat-resistant membrane and the electrolyte is 0°-5°; And / or, the longitudinal wetting value of the heat-resistant diaphragm is 3-3.5 mm, and the transverse wetting value is 2-3 mm.

[0009] In one optional embodiment, the heat-resistant membrane has an ionic conductivity of 1.4-1.6 mS / cm; a longitudinal tensile strength of 169-178 MPa and a transverse tensile strength of 163-171 MPa; and a longitudinal shrinkage rate of 1%-6.5% and a transverse shrinkage rate of 0.8%-5.5% at 130°C for 1 hour.

[0010] In one optional embodiment, at least a portion of the surface of the zirconium-boron hybrid layer is further provided with a self-healing layer, and the heat-resistant diaphragm has an ionic conductivity of 1.4-1.5 mS / cm; a longitudinal shrinkage rate of 1%-3.5% and a transverse shrinkage rate of 0.8%-1.5% at 130°C for 1 hour.

[0011] Secondly, this application provides a method for preparing the above-mentioned heat-resistant separator, comprising the following steps: S1, The base film is subjected to plasma treatment to obtain the pretreated base film; S2, a silane coupling agent, an organic ionic liquid and a pH adjuster are mixed to obtain a slurry, the slurry is coated onto at least one side of the pretreated base film and cured to obtain the coated base film; S3, zirconium alkoxide, β-dicarbonyl compound, aluminum source, nano-borate, phosphate and organic solvent are mixed to obtain zirconium boron hybrid sol. The coated base film is impregnated with the zirconium boron hybrid sol, solvent is replaced and first drying is performed to obtain the heat-resistant separator.

[0012] In an optional implementation, step S3 is followed by: S4, preparation of the self-healing coating, comprising the following steps: S41, Boron carbide nanopowder, hydrocarbon solvent, isocyanate and nano aluminum powder are mixed to obtain the oil phase component; S42, anionic surfactant, crosslinking agent, binder and water are mixed to obtain an aqueous phase component; S43, add the aqueous phase component to the oil phase component to obtain a self-healing emulsion, spray it onto at least one side of the heat-resistant membrane obtained in step S3, and then dry it to obtain a self-healing coating.

[0013] In an optional embodiment, in S41, the mass ratio of boron carbide nanopowder, hydrocarbon solvent, isocyanate, and nano-aluminum powder is 1-2:200-300:100-200:90-180. And / or, the Dv50 of the boron carbide nanopowder is 20-80 nm; And / or, the hydrocarbon solvent includes at least one of methylcyclohexane, n-heptane, n-hexane, and cyclohexane; And / or, the isocyanate includes at least one of methylcyclohexyl diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate; And / or, the Dv50 of the nano-aluminum powder is 50-80nm.

[0014] In an optional embodiment, in S42, the mass ratio of the anionic surfactant, crosslinking agent, binder, and water is 0.1-0.5: 5-20: 1-4: 250-500; And / or, the anionic surfactant includes at least one of sodium dodecyl sulfate, sodium dodecyl sulfate, sodium tridecyl sulfate, and sodium tetradecyl sulfate; And / or, the crosslinking agent includes at least one of diethylenetriamine, hexamethylenediamine, and ethylenediamine; And / or, the adhesive includes at least one of polyvinylpyrrolidone, hydroxypropyl methylcellulose, and polyvinyl alcohol.

[0015] In an optional embodiment, in S43, the volume ratio of the oil phase component to the aqueous phase component is 1-4:2-10; And / or, during the process of adding the aqueous phase component to the oil phase component, the system temperature is controlled at 0-5℃. After the addition is completed, stir for 15-30 minutes at a stirring speed of 8000-12000 rpm. And / or, the addition rate of the aqueous phase component to the oil phase component is controlled at 100-200 ml / min; And / or, the second drying is carried out under a protective atmosphere, at a temperature of 80-100°C, for a time of 30-60 minutes.

[0016] In one optional implementation, in S1, pulse-modulated radio frequency plasma is used to treat the base film; And / or, the frequency of the plasma treatment is 1-100 kHz, optionally 10-50 kHz; And / or, the peak power of the plasma treatment is 15-100W; And / or, the working pressure of the plasma treatment is 0.1-0.5 Pa; And / or, the plasma treatment has an on-time of 30-100ms, an off-time of 10-30ms, and a total treatment time of 15-20s; And / or, the material of the base film includes at least one of polyolefin, polyethylene terephthalate, polyimide, polyacrylonitrile, and cellulose base film.

[0017] In an optional embodiment, in S2, the mass ratio of the silane coupling agent, the organic ionic liquid, and the pH adjuster is 1-10:90-99:3-6; And / or, the coating thickness is 0.1-1 μm, optionally 0.1 μm; And / or, the silane coupling agent includes at least one of KH550 and KH7921; And / or, the organic ionic liquid includes at least one of imidazole ionic liquids, pyridine ionic liquids, and quaternary ammonium salt ionic liquids; optionally, the imidazole ionic liquid includes at least one of hydroxyethyl functionalized imidazole salt, ethylmethylimidazole tetrafluoroborate, bis(trifluoromethanesulfonyl)imide salt, and 1-ethyl-3-methylimidazole hexafluorophosphate; the pyridine ionic liquid includes at least one of 1-octylpyridine hexafluorophosphate, 1-hexylpyridine tetrafluoroborate, and 1-butylpyridine chloride; the quaternary ammonium salt ionic liquid includes at least one of tetrabutylammonium hexafluorophosphate, trimethylethylammonium trifluoromethanesulfonate, and tetraethylammonium tetrafluoroborate. And / or, the pH adjuster is a buffer system of acetic acid and citric acid, and the pH of the slurry is controlled at 4-6; And / or, the curing temperature is 60-80℃, and the curing time is 1-3 minutes.

[0018] In an optional embodiment, in S3, the mass ratio of the zirconium alkoxide, β-dicarbonyl compound, aluminum source, nano-borate, phosphate and organic solvent is 8-10:11-13:1-3:8-10:1-2:350-450. And / or, the impregnation time is 30-60 seconds; And / or, the solvent is replaced with water for 15-30 seconds; And / or, the zirconium alkoxide includes at least one of zirconium n-propoxide, zirconium isopropoxide, and zirconium n-butoxide; And / or, the β-dicarbonyl compound includes at least one of trifluoroacetylacetone, ethyl acetoacetate, and acetylacetone; And / or, the aluminum source includes at least one of aluminum chloride, aluminum isopropoxide, and aluminum nitrate; And / or, the nano-borate includes at least one of nano-aluminum borate, nano-zinc borate, and nano-sodium borate; And / or, the phosphate includes at least one of aluminum chromium phosphate and aluminum dihydrogen phosphate; And / or, the organic solvent comprises a polymer component and a small molecule solvent in a mass ratio of 150-200:200-250. Optionally, the polymer component comprises at least one of ammonium polyacrylate, polyethylene glycol, and polyethylene glycol monomethyl ether; and the small molecule solvent comprises at least one of isopropanol, ethylene glycol methyl ether, and ethanol.

[0019] Thirdly, this application provides a secondary battery, including the heat-resistant separator described above or the heat-resistant separator prepared by the above preparation method.

[0020] Fourthly, this application provides an electrical device including the aforementioned secondary battery.

[0021] The technical solution of this application has the following advantages: 1. The heat-resistant separator provided in this application includes a base film and a functional coating disposed on at least one side of the surface and / or interior of the base film; the longitudinal wetting value of the heat-resistant separator is greater than or equal to 2 mm, and the transverse wetting value is greater than or equal to 2 mm. This application, through the provision of the functional coating and the special control of the longitudinal / transverse wetting values ​​of the heat-resistant separator, can significantly improve the mechanical properties, heat resistance, wettability, and ionic conductivity of the separator without significantly increasing the separator thickness, without clogging the pores. Further, the functional coating is a silane self-assembled layer and a zirconium-boron hybrid layer disposed on at least one side of the surface and / or interior of the base film; wherein, the silane self-assembled layer can form an anchoring structure with the base film, improving wettability and ionic conductivity; the zirconium-boron hybrid layer, as an inorganic reinforcing layer, covers the surface of the silane self-assembled layer, improving the mechanical and heat resistance properties of the heat-resistant separator; the self-healing layer can repair microcracks, further improving the various properties of the heat-resistant separator.

[0022] Additional aspects and advantages of this application will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of this application. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0024] Figure 1 This is a SEM image of the heat-resistant diaphragm provided in Embodiment 1 of this application; Figure 2 This is a SEM image of a commercially available ceramic diaphragm. Detailed Implementation

[0025] The following embodiments are provided to better understand this application. However, the following embodiments do not constitute a limitation on the content and scope of protection of this application. Any product that is the same as or similar to this application, derived by anyone under the guidance of this application or by combining the features of this application with other prior art, falls within the scope of protection of this application.

[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having” and any variations thereof in the text of this application are intended to cover non-exclusive inclusion.

[0027] In the description of the embodiments of this application, the technical terms "first", "second", etc. are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features.

[0028] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Ranges defined in this way can include or exclude endpoints and can be arbitrarily combined; that is, any lower limit can be combined with any upper limit to form a range. In this application, unless otherwise stated, the numerical range "ab" represents a shortened representation of any combination of real numbers from a to b, where a and b are real numbers. For example, the numerical range "0-5" indicates that all real numbers between "0-5" have been listed herein, and "0-5" is merely a shortened representation of these numerical combinations. Furthermore, when a parameter is described as an integer ≥ 2, it is equivalent to disclosing that the parameter can be, for example, integers 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0029] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0030] In the description of the embodiments of this application, the term "at least one" refers to one or more (including two).

[0031] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0032] Unless otherwise specified, all experimental steps or conditions in the examples were performed according to conventional experimental procedures and conditions in the art. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0033] The following provides a detailed description of the heat-resistant diaphragm provided in this application, its preparation method, and its application.

[0034] In a first aspect, this application provides a heat-resistant membrane, including a base membrane and a functional coating disposed on at least one side surface and / or interior of the base membrane; The heat-resistant diaphragm has a longitudinal wetting value of ≥2 mm and a transverse wetting value of ≥2 mm; optionally, the heat-resistant diaphragm has a longitudinal wetting value of 3-3.5 mm and a transverse wetting value of 2-3 mm.

[0035] In one optional embodiment, the functional coating is a silane self-assembled layer and a zirconium-boron hybrid layer disposed on at least one side surface and / or interior of the base film; the contact angle between the heat-resistant membrane and the electrolyte is 0°-5°.

[0036] In one optional embodiment, the heat-resistant membrane has an ionic conductivity of 1.4-1.6 mS / cm; a longitudinal tensile strength of 169-178 MPa and a transverse tensile strength of 163-171 MPa; and a longitudinal shrinkage rate of 1%-6.5% and a transverse shrinkage rate of 0.8%-5.5% at 130°C for 1 hour.

[0037] In one optional embodiment, at least a portion of the surface of the zirconium-boron hybrid layer is further provided with a self-healing layer, and the heat-resistant diaphragm has an ionic conductivity of 1.4-1.5 mS / cm; a longitudinal shrinkage rate of 1%-3.5% and a transverse shrinkage rate of 0.8%-1.5% at 130°C for 1 hour.

[0038] The heat-resistant membrane provided in this application has a silane self-assembled layer that can form an anchoring structure with the base membrane, improving wettability and ionic conductivity; a zirconium-boron hybrid layer, as an inorganic reinforcing layer, covers the surface of the silane self-assembled layer, enhancing the mechanical and heat resistance properties of the heat-resistant membrane; and a self-healing layer that can repair microcracks, further improving the various properties of the heat-resistant membrane.

[0039] Secondly, this application provides a method for preparing a heat-resistant separator, comprising the following steps: S1, The base film is subjected to plasma treatment to obtain the pretreated base film; S2, mix silane coupling agent, organic ionic liquid and pH adjuster to obtain slurry, coat the slurry onto at least one side surface of the pretreated base film, and cure to obtain coated base film; S3, zirconium alkoxide, β-dicarbonyl compound, aluminum source, nano-borate, phosphate and organic solvent are mixed to obtain zirconium boron hybrid sol. The coated base film is impregnated with the zirconium boron hybrid sol, solvent is replaced and first drying is performed to obtain the heat-resistant membrane.

[0040] According to the above-mentioned technical means, pre-treatment of the base membrane with plasma can generate polar groups and active sites on the surface of the base membrane, which can significantly improve the wettability of the membrane and connect it with the subsequent silane-assisted assembly layer. This is the basis for improving the heat resistance, wettability, and ion mobility of the membrane. In step S2, after coating the slurry and curing, a silane-assisted assembly layer is obtained. Because the amino terminus of the silane coupling agent is pre-assembled with the polar groups, active sites, or carboxyl groups on the surface of the base membrane through hydrogen bonds, the head groups of the silane coupling agent are arranged with spacing, ensuring that only polar groups are formed on the inner wall or surface of the pores of the base membrane. Monolayer modification avoids multi-molecule accumulation and blockage, and also ensures a spaced arrangement when subsequently combined with zirconium-boron hybrid sol, preventing pore blockage. Using an organic ionic liquid as a solvent guides a more ordered arrangement of the silane coupling agent; water as a solvent would lead to excessive hydrolysis of the silane. Other organic solvents (such as DMF-type solvents) can cause swelling of the base film, affecting its performance. Impregnating the coated base film with zirconium-boron hybrid sol forms a zirconium-boron hybrid coating on its surface, effectively improving the membrane's heat resistance, wettability, and ionic conductivity. This preparation method can significantly improve the membrane's heat resistance, wettability, and ionic conductivity without significantly increasing the membrane thickness, without clogging the pores. The zirconium alkoxide and nano-borate have low thermal conductivity, creating a thermal barrier effect. Specifically, the principle of forming a zirconium-boron hybrid coating is as follows: First, the amino terminus of the silane coupling agent pre-assembles with the base film surface through hydrogen bonds, forming hydrogen bonds (≡Si-OH) between the silane head and the base film. Then, through impregnation and hydrolysis of the zirconium-boron hybrid sol (≡Si-OH + Zr(OR)4 → ≡Si-O-Zr-OR + ROH), aluminum and boron undergo condensation reactions with zirconium (Zr-OH + HO-Al → Zr-O-Al + H2O; Zr-OH + HO-B≡ → Zr-OB≡), a zirconium-boron hybrid coating that does not clog pores can be formed. The purpose of adding an aluminum source to the zirconium-boron hybrid sol is mainly to provide Al... 3+ It participates in Zr-O-Al bonding and inhibits ZrO2 phase transformation; if it is missing, it can easily cause zirconium oxide grains to grow larger, leading to a decrease in heat resistance and mechanical properties.

[0041] In an optional implementation, step S3 is followed by: S4, preparation of the self-healing coating, comprising the following steps: S41, Boron carbide nanopowder, hydrocarbon solvent, isocyanate and nano aluminum powder are mixed to obtain the oil phase component; S42, anionic surfactant, crosslinking agent, binder and water are mixed to obtain an aqueous phase component; S43, add the aqueous phase component to the oil phase component to obtain a self-healing emulsion, spray it onto at least one side of the heat-resistant membrane obtained in step S3, and then dry it to obtain a self-healing coating.

[0042] Based on the aforementioned technical methods, the self-healing coating not only functions as a flame retardant but also provides self-healing for cracks (the microcapsules rupture to release isocyanate, which reacts with water to achieve self-healing) and thermal protection (the released aluminum powder oxidizes for thermal insulation). Specifically, isocyanate provides highly active -NCO groups, and the crosslinking agent (such as ethylenediamine) has a bis-NH2-initiated interfacial polymerization (OCN-(CH2)6-NCO + H2N-(CH2)2-NH2 → [NH-CO-NH-(CH2)2]n). The isocyanate and crosslinking agent form a microcapsule structure through interfacial condensation. Boron carbide nanoparticles react with isocyanate through their surface B-OH groups, and are subsequently incorporated into the capsule wall through interfacial condensation of isocyanate and crosslinking agent when the oil-phase solution and aqueous-phase solution are mixed. Compared to direct mixing, the microcapsule structure can better retain the repairing agent and avoid its loss; it also has a better triggering mechanism, as the microcapsules actively rupture at high temperatures to release the repairing agent; and it can improve the interfacial bonding force with the zirconium-boron hybrid coating.

[0043] In this application, the prepared self-healing emulsion includes a microcapsule structure, comprising: (1) Core material: nano aluminum powder and excess isocyanate component are selected; (2) Capsule wall material: Boron carbide, isocyanate and crosslinking agent are selected; (3) Core diameter: 50-80 nm; In an optional embodiment, in S41, the mass ratio of boron carbide nanopowder, hydrocarbon solvent, isocyanate, and nano-aluminum powder is 1-2:200-300:100-200:90-180. As an example, the mass ratio of boron carbide nanopowder, hydrocarbon solvent, isocyanate, and nano-aluminum powder can be 1:200:100:90, 1.5:200:100:90, 2:200:100:90, 1:250:100:90, 1.3:280:120:150, 1.7:230:180:120, 1:300:200:180, or within any of the above ranges.

[0044] And / or, the Dv50 of the boron carbide nanoparticles is 20-80 nm; as an example, the Dv50 of the boron carbide nanoparticles can be 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, or within any range of the above values; by limiting the particle size of the boron carbide nanoparticles, this application can avoid the problem that excessively large particle sizes can easily cause powder shedding and poor bonding, or excessively small particle sizes can cause agglomeration and affect dispersibility.

[0045] And / or, the hydrocarbon solvent includes at least one of methylcyclohexane, n-heptane, n-hexane, and cyclohexane; And / or, the isocyanate includes at least one of methylcyclohexyl diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate; And / or, the Dv50 of the nano-aluminum powder is 50-80 nm. As an example, the Dv50 of the nano-aluminum powder can be 50 nm, 60 nm, 70 nm, 80 nm, or within any range of the above values; by limiting the particle size of the nano-aluminum powder, this application can ensure that it has good dispersion stability.

[0046] In an optional embodiment, in S42, the mass ratio of the anionic surfactant, crosslinking agent, binder, and water is 0.1-0.5: 5-20: 1-4: 250-500; As an example, the mass ratio of the anionic surfactant, crosslinking agent, binder, and water can be 0.1:5:1:250, 0.2:5:1:250, 0.4:5:1:250, 0.5:5:1:250, 0.1:20:4:500, 0.3:20:4:500, 0.2:10:3:400, 0.3:15:2:300, or within any of the above ranges.

[0047] And / or, the anionic surfactant includes at least one of sodium dodecyl sulfate, sodium dodecyl sulfate, sodium tridecyl sulfate, and sodium tetradecyl sulfate; And / or, the crosslinking agent includes at least one of diethylenetriamine, hexamethylenediamine, and ethylenediamine; And / or, the adhesive includes at least one of polyvinylpyrrolidone, hydroxypropyl methylcellulose, and polyvinyl alcohol.

[0048] In one optional embodiment, in S43, the volume ratio of the oil phase component to the aqueous phase component is 1-4:2-10; as an example, the volume ratio of the oil phase component to the aqueous phase component can be 1:2, 1:5, 1:8, 1:10, 2:2, 2:6, 2:7, 3:2, 3:5, 3:8, 3:10, 4:2, 4:3, 4:5, 4:7, 4:10, or within any of the above values.

[0049] And / or, the aqueous phase component is slowly added to the oil phase component at a rate controlled at 100-200 ml / min, and the system temperature is controlled at 0-5℃; as an example, the addition rate can be 100 ml / min, 300 ml / min, 500 ml / min, 700 ml / min, 100 ml / min, 120 ml / min, 150 ml / min, 180 ml / min, 200 ml / min, or within any range of the above values; the system temperature can be 0℃, 1℃, 2℃, 3℃, 4℃, 5℃, or within any range of the above values.

[0050] And / or, after addition, maintain the system temperature at 0-5℃, stir for 15-30 minutes at a stirring speed of 8000-12000 rpm; as an example, the system temperature can be 0℃, 1℃, 2℃, 3℃, 4℃, 5℃, or within any range of the above values; the stirring speed can be 8000 rpm, 9000 rpm, 10000 rpm, 11000 rpm, 12000 rpm, or within any range of the above values; the stirring time can be 15 minutes, 18 minutes, 20 minutes, 23 minutes, 25 minutes, 27 minutes, 30 minutes, or within any range of the above values.

[0051] And / or, the second drying is carried out under a protective atmosphere, at a temperature of 80-100°C, for a time of 30-60 minutes.

[0052] As an example, the protective atmosphere can be an inert atmosphere; the temperature of the second drying can be 80°C, 85°C, 90°C, 95°C, 100°C, or within any range of the above values; the time can be 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes, 60 minutes, or within any range of the above values.

[0053] In one optional implementation, in S1, pulse-modulated radio frequency plasma is used to treat the base film; And / or, the frequency of the plasma treatment is 1-100 kHz, optionally 10-50 kHz; And / or, the peak power of the plasma treatment is 15-100W; And / or, the working pressure of the plasma treatment is 0.1-0.5 Pa; And / or, the plasma treatment has an on-time of 30-100ms, an off-time of 10-30ms, and a total treatment time of 15-20s; As an example, the frequency of the plasma treatment can be 1 kHz, 5 kHz, 10 kHz, 20 kHz, 30 kHz, 40 kHz, 50 kHz, 70 kHz, 90 kHz, 100 kHz, or within any range of the above values; the peak power of the plasma treatment can be 15 W, 20 W, 30 W, 50 W, 70 W, 90 W, 100 W, or within any range of the above values; the working pressure of the plasma treatment can be 0.1 Pa, 0.2 Pa, 0.3 Pa, 0. The plasma treatment time can be 4 Pa, 0.5 Pa, or any value within the range of the above; the plasma treatment on-time can be 30 ms, 40 ms, 50 ms, 60 ms, 70 ms, 90 ms, 100 ms, or any value within the range of the above; the off-time can be 10 ms, 15 ms, 20 ms, 25 ms, 30 ms, or any value within the range of the above; the total treatment time can be 15 s, 16 s, 17 s, 18 s, 19 s, 20 s, or any value within the range of the above. This application, by adjusting the plasma treatment parameters, can minimize the impact on the mechanical strength of the diaphragm.

[0054] And / or, the base film is made of at least one of polyolefin, polyethylene terephthalate (PET), polyimide (PI), polyacrylonitrile (PAN), and cellulose base film.

[0055] In one optional embodiment, in S2, the mass ratio of the silane coupling agent, the organic ionic liquid, and the pH adjuster is 1-10:90-99:3-6; as an example, the mass ratio of the silane coupling agent, the organic ionic liquid, and the pH adjuster is 1:90:3, 1:95:4.5, 1:99:6, 3:97:4, 5:92:5, 8:94:5.5, 10:90:3, or within any of the above ranges.

[0056] And / or, the coating thickness is 0.1-1 μm, optionally 0.1 μm; as an example, the coating thickness can be 0.1 μm, 0.3 μm, 0.5 μm, 0.7 μm, 0.9 μm, 1 μm, or within any of the above values.

[0057] And / or, the silane coupling agent includes at least one of KH550 and KH7921; And / or, the organic ionic liquid includes at least one of imidazole ionic liquids, pyridine ionic liquids, and quaternary ammonium salt ionic liquids; optionally, the imidazole ionic liquid includes at least one of hydroxyethyl functionalized imidazole salt, ethylmethylimidazole tetrafluoroborate, bis(trifluoromethanesulfonyl)imide salt, and 1-ethyl-3-methylimidazole hexafluorophosphate; the pyridine ionic liquid includes at least one of 1-octylpyridine hexafluorophosphate, 1-hexylpyridine tetrafluoroborate, and 1-butylpyridine chloride; the quaternary ammonium salt ionic liquid includes at least one of tetrabutylammonium hexafluorophosphate, trimethylethylammonium trifluoromethanesulfonate, and tetraethylammonium tetrafluoroborate. And / or, the pH adjuster is a buffer system of acetic acid and citric acid (the mass ratio of the two can be 1:1 to 1:3), and the pH of the slurry is controlled at 4-6; as an example, the pH of the slurry can be 4, 4.5, 5, 5.5, 6, or within any of the above values.

[0058] And / or, the curing temperature is 60-80°C, and the curing time is 1-3 minutes. As an example, the curing temperature can be 60°C, 65°C, 70°C, 75°C, 80°C, or within any range of the above values; the curing time can be 1 minute, 1.5 minutes, 2 minutes, 2.5 minutes, 3 minutes, or within any range of the above values.

[0059] In an optional embodiment, in S3, the mass ratio of the zirconium alkoxide, β-dicarbonyl compound, aluminum source, nano-borate, phosphate and organic solvent is 8-10:11-13:1-3:8-10:1-2:350-450. And / or, the immersion time is 30-60 s; as an example, the immersion time can be 30 s, 35 s, 40 s, 45 s, 50 s, 55 s, 60 s, or within any of the above values.

[0060] And / or, the solvent replacement is performed using water for a period of 15-30 seconds; as an example, the solvent replacement time can be 15 seconds, 18 seconds, 20 seconds, 22 seconds, 25 seconds, 27 seconds, 30 seconds, or within any of the above values.

[0061] And / or, the zirconium alkoxide includes at least one of zirconium n-propoxide, zirconium isopropoxide, and zirconium n-butoxide; And / or, the β-dicarbonyl compound includes at least one of trifluoroacetylacetone, ethyl acetoacetate, and acetylacetone; And / or, the aluminum source includes at least one of aluminum chloride, aluminum isopropoxide, and aluminum nitrate; And / or, the nano-borate includes at least one of nano-aluminum borate, nano-zinc borate, and nano-sodium borate; And / or, the phosphate includes at least one of aluminum chromium phosphate (AlCr(PO4)3) and aluminum dihydrogen phosphate; And / or, the organic solvent comprises a polymer component and a small molecule solvent in a mass ratio of 150-200:200-250. Optionally, the polymer component comprises at least one of ammonium polyacrylate, polyethylene glycol, and polyethylene glycol monomethyl ether; and the small molecule solvent comprises at least one of isopropanol, ethylene glycol methyl ether, and ethanol.

[0062] This application also provides a heat-resistant diaphragm prepared by the above-described preparation method.

[0063] This application also provides a secondary battery, including the heat-resistant separator described above. Typically, but not exclusively, the secondary battery may be a lithium-ion battery or a sodium-ion battery, etc.

[0064] This application also provides an electrical device, including the aforementioned secondary battery.

[0065] Specifically, as a preferred embodiment, the method for preparing the heat-resistant separator provided in this application may include the following steps: Step 1: Plasma activation and enhancement treatment of the base film; Step 2: Preparation of coating by silane coupling agent-assisted assembly; Step 3: Preparation of zirconium-boron hybrid coating; Step 4: Preparation of self-healing coating.

[0066] Step 1 includes: Step 101: Treat the base membrane (such as a polyolefin membrane with a thickness of 5-25 μm) with plasma using pulse-modulated radio frequency plasma with a frequency range of 1-100 kHz, preferably 10-50 kHz. Step 102: Set the plasma on-time t_on to 30-100ms and the off-time t_off to 10-30ms; the total processing time is 15-20s. Step 103: Adjust the peak power P_peak of the plasma to 15-100W; Step 104: Control the working pressure of the plasma to 0.1-0.5 Pa.

[0067] Step 2 includes: Step 201: Prepare the coating slurry, comprising the following components: (1) Main film-forming agent: Select one or a mixture of two of KH550 and KH7921; (2) Organic ionic liquids: including at least one of imidazole ionic liquids, pyridine ionic liquids, and quaternary ammonium salt ionic liquids; optionally, the imidazole ionic liquids include, but are not limited to, at least one of hydroxyethyl functionalized imidazole salts, ethylmethylimidazole tetrafluoroborate, bis(trifluoromethanesulfonyl)imide salts, and 1-ethyl-3-methylimidazole hexafluorophosphate; the pyridine ionic liquids include, but are not limited to, at least one of 1-octylpyridine hexafluorophosphate, 1-hexylpyridine tetrafluoroborate, and 1-butylpyridine chloride; the quaternary ammonium salt ionic liquids include, but are not limited to, at least one of tetrabutylammonium hexafluorophosphate, trimethylethylammonium trifluoromethanesulfonate, and tetraethylammonium tetrafluoroborate; (3) pH adjuster: A buffer system of acetic acid and citric acid is used, and the pH value of the system is controlled within the range of 4-6; (4) The main film-forming agent, organic ionic liquid and pH adjuster are mixed in a weight ratio of 1-10:90-99:3-6 to obtain the coating slurry; Step 202: The treated diaphragm is coated with a coating using a micro-gravure automatic roller coating equipment. The coating thickness is controlled between 0.1-1 μm, preferably 0.1 μm. Step 203: Curing at 60-80℃ for 1-3 minutes.

[0068] Step 3 includes: Step 301: Prepare the zirconium-boron hybrid sol formulation, including: (1) Prepare a mixed sol of zirconium alkoxide, β-dicarbonyl compound (e.g., acetylacetone) and aluminum source, wherein the weight ratio of zirconium propoxide, acetylacetone and aluminum nitrate is 8-10:11-13:1-3; (2) Add nano aluminum borate and phosphate (aluminum dihydrogen phosphate) in a weight ratio of 8-10:1-2; (3) Solvent: The weight ratio of the mixed solution of polyethylene glycol monomethyl ether and ethanol is 150-200: 200-250; Step 302: Impregnate the coated base film obtained in step 2 with the above-mentioned zirconium-boron hybrid sol for 30-60 seconds; Step 303: Introduce ultrapure water as the replacement solvent and replace for 15-30 seconds; Step 304: Use a hot air knife to dry the diaphragm to obtain a zirconium-boron hybrid layer; Step 4 includes: Step 401: Prepare a self-repairing emulsion, comprising a microcapsule structure, wherein the microcapsules include: (1) Core material: nano aluminum powder and excess isocyanate component are selected; (2) Capsule wall material: Boron carbide, isocyanate and crosslinking agent are selected; (3) Core diameter: 50-80 nm; (4) Preparation of oil phase system: Boron carbide nanopowder and cyclohexane solvent are ultrasonically dispersed evenly; hexamethylene diisocyanate is added and magnetically stirred until completely dissolved to form a transparent solution. Nano aluminum powder is added to the transparent solution and premixed by high-speed shearing to obtain gray oil phase component A; the mass ratio of boron carbide nanopowder, cyclohexane solvent, hexamethylene diisocyanate and nano aluminum powder is 1-2:200-300:100-200:90-180; (5) Preparation of aqueous phase system: Polyvinyl alcohol and deionized water are dissolved in a water bath at 60-80℃ with magnetic stirring and then cooled to room temperature at 15-25℃; ethylenediamine and sodium dodecyl sulfate are added and stirred until clear to obtain aqueous phase component B. The mass ratio of polyvinyl alcohol, deionized water, ethylenediamine and sodium dodecyl sulfate is 1-4:250-500:5-20:0.1-0.5.

[0069] (6) Emulsion construction and polymerization: Transfer oil phase component A to the reactor, and then slowly add aqueous phase component B at 100-200 ml / min. The volume ratio of oil phase to aqueous phase is 1-4:2-10. The cooling circulation temperature is 0-5℃ throughout the process. After the addition is completed, the stirring speed is set to 8000-12000 rpm for 15-30 min.

[0070] Step 402: The self-healing emulsion can be evenly distributed on the surface of the zirconium-boron hybrid coating using electrostatic spraying technology; Step 403: Control the spraying parameters: (1) Nozzle diameter: 0.5-1mm; (2) Spray rate: 5-10 mL / min; (3) Distance: 10-20cm; Step 404: Under an inert atmosphere, heat to 80-100℃ and maintain for 30-60 minutes to achieve the construction of the self-healing layer.

[0071] Those skilled in the art will understand that the secondary battery provided in this application, taking a lithium-ion battery as an example, includes, in addition to the aforementioned heat-resistant separator, structural components such as a positive electrode, a negative electrode, an electrolyte, and a casing. During the charging and discharging process, lithium ions repeatedly insert and extract between the positive and negative electrodes. The electrolyte acts as a conductor between the positive and negative electrodes. The separator, positioned between the positive and negative electrodes, primarily prevents short circuits between the positive and negative electrodes while allowing lithium ions to pass through.

[0072] As an example, the positive electrode sheet includes a positive current collector and a positive active layer. The positive current collector has two opposing surfaces in its own thickness direction, and the positive active layer is disposed on either or both of the opposing surfaces of the positive current collector. The materials, composition, and manufacturing methods of the positive electrode sheet used in the lithium-ion battery of this application may include any techniques disclosed in the prior art.

[0073] As an example, the negative electrode sheet includes a negative electrode current collector and a negative electrode active layer. The negative electrode current collector has two opposing surfaces in its own thickness direction, and the negative electrode active layer is disposed on either or both of the opposing surfaces of the negative electrode current collector. The materials, composition, and manufacturing methods of the negative electrode sheet used in the lithium-ion battery of this application may include any techniques disclosed in the prior art.

[0074] The materials and shapes of the separators used in the lithium-ion batteries of this application are not particularly limited, and may include any techniques disclosed in the prior art.

[0075] Those skilled in the art will understand that the electrolyte plays a role in conducting ions between the positive and negative electrodes, and the electrolyte used in the lithium-ion battery of this application can include any technology disclosed in the prior art. As an example, the electrolyte may include lithium salts, solvents, etc. In some embodiments, the electrolyte may also optionally include additives. For example, additives may include negative electrode film-forming additives, positive electrode film-forming additives, and may also include additives that can improve certain battery performance, such as additives that improve battery overcharge performance, additives that improve battery high-temperature or low-temperature performance, etc.

[0076] This application does not specify a particular method for preparing lithium-ion batteries; conventional methods in the art can be used to prepare lithium-ion batteries. For example, a positive electrode, a separator, and a negative electrode can be stacked sequentially, with the separator positioned between the positive and negative electrodes. A cell can be obtained through a stacking or winding process, followed by baking, electrolyte injection, formation, and encapsulation to obtain the lithium-ion battery of this application.

[0077] It is understood that in the electrical equipment provided in this application, the lithium-ion battery can be used as a power source for the electrical equipment, or as an energy storage unit for the electrical equipment. The electrical equipment may be, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships and satellites, energy storage systems, etc.

[0078] The electrical equipment provided in this application has the same advantages as the aforementioned secondary batteries because it uses the secondary battery provided in this application, which will not be repeated here.

[0079] The present application will now be described with reference to specific embodiments. It should be noted that these embodiments are merely descriptive and do not limit the present application in any way.

[0080] Example 1 This embodiment provides a heat-resistant membrane, the specific preparation method and operating parameters of which are as follows: Step 1: Plasma activation and enhancement treatment; Step 101: The polyethylene diaphragm (7 μm thick) is subjected to plasma treatment using pulsed modulated radio frequency plasma with a frequency range of 25 Hz; Step 102: Set the plasma on-time t_on to 80ms and the off-time t_off to 20ms; the total processing time is 20s. Step 103: Adjust the peak power P_peak of the plasma to 50W; Step 104: Control the working pressure of the plasma to 0.3 Pa.

[0081] Step 2, Preparation of coating with silane coupling agent-assisted assembly: Step 201: Prepare a silane coating slurry, comprising the following components: (1) Main film-forming agent: KH550 silane coupling agent was selected as the main film-forming agent; (2) Solvent: 1-Ethyl-3-methylimidazolium hexafluorophosphate was selected; (3) pH adjuster: A buffer system of acetic acid and citric acid in a mass ratio of 1:3 is used, and the pH value is controlled at 5; (4) The main film-forming agent, organic ionic liquid and pH adjuster are mixed in a weight ratio of 1:99:6 to obtain the coating slurry; Step 202: The plasma-enhanced diaphragm is coated with a coating using a micro-gravure automatic roller coating equipment, and the coating thickness is controlled at 0.1 μm; Step 203: Curing at 60°C for 3 minutes.

[0082] Step 3: Preparation of zirconium-boron hybrid coating: Step 301: Prepare the zirconium-boron hybrid sol formulation, including: (1) Prepare a mixed sol of zirconium propoxide, acetylacetone and aluminum nitrate, wherein the weight ratio of zirconium propoxide, acetylacetone and aluminum nitrate is 10:11:1; (2) Add aluminum borate nanowires (average diameter of 20 nm, aspect ratio of 5:1) and aluminum dihydrogen phosphate, and control the weight ratio to 10:1; (3) Solvent: The weight ratio of the mixed solution of polyethylene glycol monomethyl ether and ethanol is 200:250; Step 302: Impregnate the coated polyolefin membrane with the above-mentioned zirconium-boron hybrid sol for 60 seconds; Step 303: Introduce ultrapure water as the replacement solvent and replace for 30 seconds; Step 304: Use a hot air knife to dry the polyolefin membrane to obtain a zirconium-boron hybrid layer; Step 4: Construction of the self-healing layer: Step 401: Prepare a self-repairing emulsion, including: (1) Core material: nano aluminum powder and excess isocyanate component are selected; (2) Capsule wall material: Boron carbide, isocyanate and crosslinking agent are selected; (3) Core diameter: 70 nm; (4) Preparation of oil phase system: Boron carbide nanopowder (Dv50 is 80nm) and cyclohexane solvent are ultrasonically dispersed evenly; hexamethylene diisocyanate is added and magnetically stirred until completely dissolved to form a transparent solution. Nano aluminum powder (Dv50 is 50nm) is added to the transparent solution and high-speed shear premixed to obtain gray oil phase component A; the mass ratio of boron carbide nanopowder, cyclohexane solvent, hexamethylene diisocyanate and nano aluminum powder is 1:200:100:180; (5) Preparation of aqueous phase system: Polyvinyl alcohol and deionized water were dissolved by magnetic stirring in a water bath at 80°C and then cooled to room temperature of 25°C; ethylenediamine and sodium dodecyl sulfate were added and stirred until clear to obtain aqueous phase component B, with the mass ratio of polyvinyl alcohol, deionized water, ethylenediamine and sodium dodecyl sulfate being 2:500:10:0.1.

[0083] (6) Emulsion construction and polymerization: The oil phase component A was transferred to the reactor, and then the aqueous phase component B was slowly added at a rate of 200 ml / min. The volume ratio of oil phase to aqueous phase was 1:2. The cooling circulation temperature was 5°C. After the addition was completed, the stirring speed was set to 8000 rpm for 15 min.

[0084] Step 402: The self-healing emulsion is evenly distributed on the surface of the zirconium-boron hybrid coating using electrostatic spraying technology; Step 403: Control the spraying parameters: (1) Nozzle diameter: 0.5 mm; (2) Spray rate: 5 mL / min; (3) Distance: 20cm; Step 404: Under an inert atmosphere, heat to 80℃ and maintain for 30 minutes to construct the self-healing layer, obtaining a heat-resistant membrane. Its SEM image is shown below. Figure 1 As shown, from Figure 1 and Figure 2The comparison shows that the heat-resistant membrane prepared in this embodiment, due to the silane-assisted assembly layer, prevents the nanoparticles of the zirconium-boron hybrid coating from accumulating and clogging the pores. Instead, they combine with the silane-assisted assembly layer, ensuring that the porosity and ionic conductivity of the base membrane do not decrease significantly. Figure 2 Commercially available (Enjie) ceramic-coated diaphragms can clog the original pores of the base membrane after coating.

[0085] Example 2 This embodiment provides a heat-resistant membrane, the specific preparation method and operating parameters of which are as follows: Step 1: Plasma activation and enhancement treatment; Step 101: The polyethylene diaphragm (7 μm thick) is subjected to plasma treatment using pulsed modulated radio frequency plasma with a frequency range of 1 kHz. Step 102: Set the plasma on-time t_on to 100ms and the off-time t_off to 10ms; the total processing time is 15s. Step 103: Adjust the peak power P_peak of the plasma to 100W; Step 104: Control the working pressure of the plasma to 0.1 Pa.

[0086] Step 2, Preparation of coating with silane coupling agent-assisted assembly: Step 201: Prepare a silane coating slurry, comprising the following components: (1) Main film-forming agent: KH550 silane coupling agent was selected as the main film-forming agent; (2) Solvent: 1-Ethyl-3-methylimidazolium hexafluorophosphate was selected; (3) pH adjuster: A buffer system of acetic acid and citric acid in a mass ratio of 1:3 was used, and the pH value of the system was controlled at 6; (4) The main film-forming agent, organic ionic liquid and pH adjuster are mixed in a weight ratio of 10:90:3 to obtain the coating slurry; Step 202: The plasma-enhanced diaphragm is coated with a coating using a micro-gravure automatic roller coating equipment, and the coating thickness is controlled at 1μm. Step 203: Curing at 60°C for 3 minutes.

[0087] Step 3: Preparation of zirconium-boron hybrid coating: Step 301: Prepare the zirconium-boron hybrid sol formulation, including: (1) Prepare a mixed sol of zirconium propoxide, acetylacetone and aluminum nitrate, wherein the weight ratio of zirconium propoxide, acetylacetone and aluminum nitrate is 8:13:3; (2) Add aluminum borate nanowires (average diameter of 20 nm, aspect ratio of 5:1) and aluminum dihydrogen phosphate, and control the weight ratio to 8:2; (3) Solvent: The weight ratio of the mixed solution of polyethylene glycol monomethyl ether and ethanol is 150:200; Step 302: Impregnate the coated polyolefin membrane with the above-mentioned zirconium-boron hybrid sol for 30 seconds; Step 303: Introduce ultrapure water as the replacement solvent and replace for 15 seconds; Step 304: Use a hot air knife to dry the polyolefin membrane to obtain a zirconium-boron hybrid layer; Step 4: Construction of the self-healing layer: Step 401: Prepare a self-repairing emulsion, including: (1) Core material: nano aluminum powder and excess isocyanate component are selected; (2) Capsule wall material: Boron carbide, isocyanate and crosslinking agent are selected; (3) Core diameter: 80 nm; (4) Preparation of oil phase system: Boron carbide nanopowder (Dv50 is 80nm) and cyclohexane solvent are ultrasonically dispersed evenly; hexamethylene diisocyanate is added and magnetically stirred until completely dissolved to form a transparent solution. Nano aluminum powder (Dv50 is 50nm) is added to the transparent solution and high-speed shear premixed to obtain gray oil phase component A; the mass ratio of boron carbide nanopowder, cyclohexane solvent, hexamethylene diisocyanate and nano aluminum powder is 2:300:200:90; (5) Preparation of aqueous phase system: Polyvinyl alcohol and deionized water were dissolved by magnetic stirring in a water bath at 60°C and then cooled to room temperature of 15°C; ethylenediamine and sodium dodecyl sulfate were added and stirred until clear to obtain aqueous phase component B, with the mass ratio of polyvinyl alcohol, deionized water, ethylenediamine and sodium dodecyl sulfate being 1:250:5:0.5.

[0088] (6) Emulsion construction and polymerization: The oil phase component A was transferred to the reactor, and then the aqueous phase component B was slowly added at a rate of 100 ml / min. The volume ratio of oil phase to aqueous phase was 4:10. The cooling circulation temperature was 0℃ throughout the process. After the addition was completed, the stirring speed was set to 12000 rpm for 30 min.

[0089] Step 402: The self-healing emulsion is evenly distributed on the surface of the zirconium-boron hybrid coating using electrostatic spraying technology; Step 403: Control the spraying parameters: (1) Nozzle diameter: 1mm; (2) Spray rate: 10 mL / min; (3) Distance: 10cm; Step 404: Under an inert atmosphere, heat to 100°C and maintain for 60 minutes to achieve the construction of the self-healing layer and obtain a heat-resistant diaphragm.

[0090] Example 3 This embodiment provides a heat-resistant membrane, the specific preparation method and operating parameters of which are as follows: Step 1: Plasma activation and enhancement treatment; Step 101: The polyolefin membrane (7 μm thick) is subjected to plasma treatment using pulsed modulated radio frequency plasma with a frequency range of 100 Hz. Step 102: Set the plasma on-time t_on to 30ms and the off-time t_off to 30ms; the total processing time is 20s. Step 103: Adjust the peak power P_peak of the plasma to 15W; Step 104: Control the working pressure of the plasma to 0.5 Pa.

[0091] Step 2, Preparation of coating with silane coupling agent-assisted assembly: Step 201: Prepare a silane coating slurry, comprising the following components: (1) Main film-forming agent: KH550 silane coupling agent was selected as the main film-forming agent; (2) Solvent: 1-Ethyl-3-methylimidazolium hexafluorophosphate was selected; (3) pH adjuster: A buffer system of acetic acid and citric acid in a mass ratio of 1:3 was used, and the pH value of the system was controlled at 4; (4) The main film-forming agent, organic ionic liquid and pH adjuster are mixed in a weight ratio of 5:95:4 to obtain the coating slurry; Step 202: The plasma-enhanced diaphragm is coated with a coating using a micro-gravure automatic roller coating equipment, and the coating thickness is controlled at 0.5 μm; Step 203: Curing at 70°C for 2 minutes.

[0092] Step 3: Preparation of zirconium-boron hybrid coating: Step 301: Prepare the zirconium-boron hybrid sol formulation, including: (1) Prepare a mixed sol of zirconium propoxide, acetylacetone and aluminum nitrate, wherein the weight ratio of zirconium propoxide, acetylacetone and aluminum nitrate is 9:12:2; (2) Add aluminum borate nanowires (average diameter of 20 nm, aspect ratio of 5:1) and aluminum dihydrogen phosphate, and control the weight ratio to 9:1.5; (3) Solvent: The weight ratio of the mixed solution of polyethylene glycol monomethyl ether and ethanol is 180:230; Step 302: Impregnate the coated polyolefin membrane with the above-mentioned zirconium-boron hybrid sol for 45 seconds; Step 303: Introduce ultrapure water as the replacement solvent and replace for 20 seconds; Step 304: Use a hot air knife to dry the polyolefin membrane to obtain a zirconium-boron hybrid layer; Step 4: Construction of the self-healing layer: Step 401: Prepare a self-repairing emulsion, including: (1) Core material: nano aluminum powder and excess isocyanate component are selected; (2) Capsule wall material: Boron carbide, isocyanate and crosslinking agent are selected; (3) Core diameter: 65 nm; (4) Preparation of oil phase system: Boron carbide nanopowder (Dv50 is 80nm) and cyclohexane solvent are ultrasonically dispersed evenly; hexamethylene diisocyanate is added and magnetically stirred until completely dissolved to form a transparent solution. Nano aluminum powder (Dv50 is 50nm) is added to the transparent solution and high-speed shear premixed to obtain gray oil phase component A; the mass ratio of boron carbide nanopowder, cyclohexane solvent, hexamethylene diisocyanate and nano aluminum powder is 1.5:250:1500:120; (5) Preparation of aqueous phase system: Polyvinyl alcohol and deionized water were dissolved by magnetic stirring in a water bath at 70°C and then cooled to room temperature of 20°C; ethylenediamine and sodium dodecyl sulfate were added and stirred until clear to obtain aqueous phase component B, with the mass ratio of polyvinyl alcohol, deionized water, ethylenediamine and sodium dodecyl sulfate being 4:500:20:0.1.

[0093] (6) Emulsion construction and polymerization: The oil phase component A was transferred to the reactor, and then the aqueous phase component B was slowly added at 100 ml / min. The volume ratio of oil phase to aqueous phase was 3:5. The cooling circulation temperature was 3℃, and the stirring speed was set to 10000 rpm for 20 min.

[0094] Step 402: The self-healing emulsion is evenly distributed on the surface of the zirconium-boron hybrid coating using electrostatic spraying technology; Step 403: Control the spraying parameters: (1) Nozzle diameter: 0.8 mm; (2) Spray rate: 8 mL / min; (3) Distance: 15cm; Step 404: Under an inert atmosphere, heat to 90°C and maintain for 40 minutes to achieve the construction of the self-healing layer and obtain a heat-resistant diaphragm.

[0095] Example 4 This embodiment provides a heat-resistant membrane, which differs from Embodiment 1 in that the raw materials selected and proportioned in the coating slurry in step 2 are: the mass ratio of the main film-forming agent KH7921, the organic ionic liquid 1-butylpyridine chloride, and the pH adjuster is 6:95:4.

[0096] Example 5 This embodiment provides a heat-resistant diaphragm, which differs from Embodiment 1 in that the raw material selection and ratio in the zirconium-boron hybrid sol in step 3 is as follows: the mass ratio of zirconium isopropoxide, β-dicarbonyl compound ethyl acetoacetate, aluminum source aluminum isopropoxide, aluminum borate nanowires, aluminum chromium phosphate, polyethylene glycol, and isopropanol is 9:12:2:9:1.5:170:240.

[0097] Example 6 This embodiment provides a heat-resistant diaphragm, which differs from Embodiment 1 in that the raw material selection and ratio in the zirconium-boron hybrid sol in step 3 is as follows: the mass ratio of zirconium n-butoxide, β-dicarbonyl compound trifluoroacetylacetone, aluminum source aluminum chloride, aluminum borate nanowires, aluminum chromium phosphate, ammonium polyacrylate, and ethylene glycol methyl ether is 8.5:12.5:1.5:9.5:1.2:190:220.

[0098] Example 7 This embodiment provides a heat-resistant membrane, which differs from Embodiment 1 in that the volume ratio of the oil phase component to the water phase component in step 3 is 3:3.

[0099] Example 8 This embodiment provides a heat-resistant membrane, which differs from Embodiment 1 in that the volume ratio of the oil phase component to the water phase component in step 3 is 3:7.

[0100] Example 9 This embodiment provides a heat-resistant membrane, which differs from Embodiment 1 in that it does not include step 4, i.e., it does not have a self-healing layer.

[0101] Comparative Example 1 This comparative example provides a heat-resistant diaphragm, which differs from Example 1 in that only steps 1 and 2 are performed.

[0102] Comparative Example 2 A polyolefin membrane of the same thickness and composition as the base membrane.

[0103] Comparative Example 3 This comparative example provides a heat-resistant diaphragm, which differs from Example 1 in that it does not include the treatment in step 1.

[0104] Comparative Example 4 This comparative example provides a heat-resistant diaphragm, which differs from Example 1 in that it does not include the treatment in step 2.

[0105] Comparative Example 5 This comparative example provides a heat-resistant diaphragm, which differs from Example 1 in that it does not include the treatment in step 1.

[0106] Experimental Example 1 Performance tests were conducted on the heat-resistant membranes provided in each embodiment and comparative example. The specific test items and methods are as follows: (1) Thermal shrinkage rate Referring to GB / T 36363-2018 "Polyolefin Separators for Lithium-ion Batteries", three 100mm × 100mm films were cut. Each sample was placed between two sheets of quantitative filter paper and then in the center of a blower-type constant temperature chamber. The longitudinal (MD) and transverse (TD) length changes of the film before and after heating were measured. The test conditions were: temperature 130℃, test duration 1 hour.

[0107] (2) Tensile strength The test shall be conducted in accordance with the provisions of GB / T1040.3-2006, using three specimens with a width of 15 mm, an initial distance of 100 mm between the fixtures, and a test speed of 250 mm / min.

[0108] (3) Ionic conductivity The electrochemical impedance spectroscopy (EIS) method was used to test the coin cells assembled in an argon glove box. The electrolyte was 1M LiPF6 / ethylene carbonate (EC) and dimethyl carbonate (DMC) (volume ratio 1:1). The electrochemical workstation had a frequency of 0.1Hz-100kHz and an amplitude of 10mV. The cells were allowed to stand for 24 hours before testing to allow the electrolyte to fully impregnate them.

[0109] (4) Electrolyte contact angle The instantaneous morphology of droplets was captured using a contact angle meter, according to ISO 19403-7, "Measurement of wettability". Five 25mm × 100mm thin films were cut, and the test liquid was 1M LiPF6 / EC:DMC (1:1); the titration rate was 2μL / drop. Each 2μL drop was applied to the sample surface using a syringe. The sample size was 25mm × 100mm, and the samples were secured to a glass slide with double-sided tape. A high-precision contact angle meter was used to record the instantaneous contact angle formed by the liquid on the diaphragm sample surface. A smaller contact angle indicates that the liquid more easily wets the diaphragm sample surface.

[0110] (5) Infiltration value Cut the diaphragm into a 50mm long and 50mm wide sample, and mark the longitudinal (MD) and transverse (TD) directions. Lay the diaphragm flat on a glass slide and secure it at the four corners with green tape. Using a 1mL syringe, add a single drop of electrolyte with a volume of 2μL. Observe the changes in MD and TD dimensions of the droplet at 0 min and 5 min using a digital microscope at 20x magnification.

[0111] The specific test results are shown in the table below: Table 1

[0112] As can be seen from the test results in the table above, the heat-resistant diaphragm provided in this application embodiment has the characteristics of good wettability, high tensile strength, and low thermal shrinkage; its electrolyte contact angle is 0°; the tensile strength MD≥169.3MPa, TD≥163.0MPa; the thermal shrinkage rate at 130℃ / 1h MD≤6.4%, TD≤5.5%; the ionic conductivity ≥1.4 mS / cm, and the TD and MD wetting values ​​are greater than 2mm.

[0113] Compared to Example 1, the PE base film of Comparative Example 1 did not have a zirconium-boron hybrid coating and a self-healing layer prepared on its surface, resulting in a larger contact angle, poor wettability, and a larger thermal shrinkage rate.

[0114] Compared to Example 1, Comparative Example 2 was not treated in any way, and it had a larger contact angle, poorer wettability, and a larger thermal shrinkage rate.

[0115] Compared to Example 1, Comparative Example 3 did not undergo plasma treatment, which resulted in the subsequent coating not being effectively adsorbed and bonded, leading to a larger contact angle, poor wettability, and a larger thermal shrinkage rate.

[0116] Compared to Example 1, Comparative Example 4 did not undergo zirconium-boron hybrid coating treatment, resulting in a larger contact angle (which can be slightly improved due to plasma treatment), poor wettability, and although the thermal shrinkage rate was somewhat improved due to the self-healing layer, the effect was not good.

[0117] Compared to Example 1, Comparative Example 5 did not undergo plasma treatment or self-healing layer coating. Consequently, the corresponding zirconium-boron hybrid coating could not effectively adhere to and bond with the base film, resulting in a larger contact angle, poorer wettability, and a larger thermal shrinkage rate.

[0118] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A heat resistant diaphragm, characterized by, The base film and a functional coating layer arranged on at least one side surface and / or inside of the base film; The longitudinal wetting value of the heat-resistant diaphragm is greater than or equal to 2mm, and the transverse wetting value is greater than or equal to 2mm.

2. The heat resistant diaphragm of claim 1, wherein, The functional coating layer is a silane self-assembled layer and a zirconium-boron hybrid layer arranged on at least one side surface and / or inside of the base film; the contact angle of the heat-resistant diaphragm with the electrolyte is 0-5°; And / or, the longitudinal wetting value of the heat-resistant diaphragm is 3-3.5mm, and the transverse wetting value is 2-3mm.

3. The heat resistant diaphragm of claim 1, wherein, The ion conductivity of the heat-resistant diaphragm is 1.4-1.6mS / cm; the longitudinal tensile strength is 169-178MPa, and the transverse tensile strength is 163-171MPa; the longitudinal shrinkage rate at 130℃ for 1h is 1%-6.5%, and the transverse shrinkage rate is 0.8%-5.5%.

4. The heat resistant diaphragm according to any one of claims 1 to 3, characterized in that, At least part of the surface of the zirconium-boron hybrid layer is further provided with a self-repairing layer, and the ion conductivity of the heat-resistant diaphragm is 1.4-1.5mS / cm; the longitudinal shrinkage rate at 130℃ for 1h is 1%-3.5%, and the transverse shrinkage rate is 0.8%-1.5%.

5. A method of producing the heat-resistant diaphragm according to any one of claims 1 to 4, characterized by, The method comprises the following steps: S1, the base film is subjected to plasma treatment to obtain a pretreated base film; S2, a silane coupling agent, an organic ionic liquid and a pH adjuster are mixed to obtain a slurry, and the slurry is coated on at least one side surface of the pretreated base film and solidified to obtain a coated base film; S3, an alcoholate of zirconium, a beta-dicarbonyl compound, an aluminum source, a nanometer borate, a phosphate, and an organic solvent are mixed to obtain a zirconium-boron hybrid sol, and the coated base film is immersed in the zirconium-boron hybrid sol, solvent is replaced, and first drying is performed to obtain the heat-resistant diaphragm.

6. The method of claim 5, wherein the heat resistant diaphragm is prepared by the steps of: After step S3, it further comprises: S4, self-repairing coating preparation, comprising the following steps: S41, boron carbide nanometer powder, hydrocarbon solvent, isocyanate and nanometer aluminum powder are mixed to obtain an oil phase component; S42, an anionic surfactant, a crosslinking agent, a binder and water are mixed to obtain an aqueous phase component; S43, the aqueous phase component is added to the oil phase component to obtain a self-repairing emulsion, which is sprayed on at least one side surface of the heat-resistant diaphragm obtained in step S3, and second drying is performed to obtain a self-repairing coating.

7. The method of claim 6, wherein the heat resistant diaphragm is prepared by the steps of: In S41, the mass ratio of the boron carbide nanometer powder, the hydrocarbon solvent, the isocyanate, and the nanometer aluminum powder is 1-2:200-300:100-200:90-180; And / or, the Dv50 of the boron carbide nanometer powder is 20-80nm; And / or, the hydrocarbon solvent comprises at least one of methylcyclohexane, n-heptane, n-hexane, and cyclohexane; And / or, the isocyanate comprises at least one of methylcyclohexyl diisocyanate, isophorone diisocyanate, and hexamethylene diisocyanate; And / or, the Dv50 of the nanometer aluminum powder is 50-80nm.

8. The method of claim 6, wherein the heat resistant diaphragm is prepared by the steps of: In S42, the mass ratio of the anionic surfactant, the crosslinking agent, the binder, and the water is 0.1-0.5:5-20:1-4:250-500; And / or, the anionic surfactant comprises at least one of sodium dodecyl sulfonate, sodium dodecyl sulfate, sodium tridecyl sulfate, and sodium tetradecyl sulfate; And / or, the crosslinking agent comprises at least one of diethylene triamine, hexanediamine, ethylenediamine; And / or, the binder comprises at least one of polyvinylpyrrolidone, hydroxypropyl methyl cellulose, polyvinyl alcohol.

9. The method of claim 6, wherein the heat resistant diaphragm is prepared by the steps of: In S43, the volume ratio of the oil phase component and the water phase component is 1-4:2-10; And / or, during the process of adding the water phase component into the oil phase component, the temperature of the system is controlled at 0-5℃, and after the addition is completed, the stirring is carried out for 15-30min at a stirring speed of 8000-12000rpm; And / or, the adding speed of the water phase component into the oil phase component is controlled at 100-200ml / min; And / or, the second drying is carried out in a protective atmosphere, and the temperature of the second drying is 80-100℃, and the time of the second drying is 30-60min.

10. The method of claim 5-9, wherein the heat resistant diaphragm is prepared by the steps of: In S1, the base film is treated by pulse modulation radio frequency plasma; And / or, the frequency of the plasma treatment is 1-100kHz, and optionally 10-50kHz; And / or, the peak power of the plasma treatment is 15-100W; And / or, the working gas pressure of the plasma treatment is 0.1-0.5Pa; And / or, the opening time of the plasma treatment is 30-100ms, the closing time is 10-30ms, and the total treatment time is 15-20s; And / or, the material of the base film comprises at least one of polyolefin, polyethylene terephthalate, polyimide, polyacrylonitrile, cellulose-based film.

11. The method of claim 5-9, wherein the heat resistant diaphragm is prepared by the steps of: In S2, the mass ratio of the silane coupling agent, the organic ionic liquid and the pH regulator is 1-10:90-99:3-6; And / or, the thickness of the coating is 0.1-1μm, and optionally 0.1μm; And / or, the silane coupling agent comprises at least one of KH550 and KH7921; And / or, the organic ionic liquid comprises at least one of imidazole ionic liquid, pyridine ionic liquid, quaternary ammonium salt ionic liquid; optionally, the imidazole ionic liquid comprises at least one of hydroxyethyl functionalized imidazole salt, ethylmethyl imidazole tetrafluoroborate, bis-trifluoromethanesulfonylimide salt, 1-ethyl-3-methyl imidazole hexafluorophosphate; the pyridine ionic liquid comprises at least one of 1-octyl pyridine hexafluorophosphate, 1-hexyl pyridine tetrafluoroborate, 1-butyl pyridine chloride; the quaternary ammonium salt ionic liquid comprises at least one of tetrabutylammonium hexafluorophosphate, trimethylethylammonium triflate, tetraethylammonium tetrafluoroborate; And / or, the pH regulator adopts a buffer system mixed by acetic acid and citric acid, and the pH of the slurry is controlled at 4-6; And / or, the temperature of the solidification is 60-80℃, and the solidification time is 1-3min.

12. The method of claim 5-9, wherein the heat resistant diaphragm is prepared by the steps of: In S3, the mass ratio of the zirconium alkoxide, the β-dicarbonyl compound, the aluminum source, the nano borate, the phosphate and the organic solvent is 8-10:11-13:1-3:8-10:1-2:350-450; And / or, the time of the impregnation is 30-60s; And / or, the solvent replacement is carried out by using water, and the replacement time is 15-30s; And / or, the alcoholate of zirconium includes at least one of zirconium n-propylate, zirconium isopropylate, zirconium n-butyrate; And / or, the β-dicarbonyl compound includes at least one of trifluoroacetylacetone, ethyl acetoacetate, acetylacetone; And / or, the aluminum source includes at least one of aluminum chloride, aluminum isopropylate, aluminum nitrate; And / or, the nano borate includes at least one of nano aluminum borate, nano zinc borate, nano sodium borate; And / or, the phosphate includes at least one of aluminum chromium phosphate, aluminum dihydrogen phosphate; And / or, the organic solvent includes polymer components and small molecule solvents in a mass ratio of 150-200:200-250, optionally, the polymer components include at least one of ammonium polyacrylate, polyethylene glycol, polyethylene glycol monomethyl ether; the small molecule solvent includes at least one of isopropyl alcohol, ethylene glycol methyl ether, ethanol.

13. A secondary battery characterized by comprising: The heat-resistant diaphragm prepared by the preparation method of any one of claims 1-4.

14. An electrical device, characterized by The secondary battery of claim 13.

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